diff --git a/atom/browser/api/atom_api_session.cc b/atom/browser/api/atom_api_session.cc
index 3ca15ab871f..7d31626c141 100644
--- a/atom/browser/api/atom_api_session.cc
+++ b/atom/browser/api/atom_api_session.cc
@@ -233,16 +233,16 @@ void SetProxyInIO(net::URLRequestContextGetter* getter,
 Session::Session(AtomBrowserContext* browser_context)
     : browser_context_(browser_context) {
   AttachAsUserData(browser_context);
+
   // Observe DownloadManger to get download notifications.
-  auto download_manager =
-      content::BrowserContext::GetDownloadManager(browser_context);
-  download_manager->AddObserver(this);
+  content::BrowserContext::GetDownloadManager(browser_context)->
+      AddObserver(this);
 }
 
 Session::~Session() {
-  auto download_manager =
-      content::BrowserContext::GetDownloadManager(browser_context_);
-  download_manager->RemoveObserver(this);
+  content::BrowserContext::GetDownloadManager(browser_context())->
+      RemoveObserver(this);
+  Destroy();
 }
 
 void Session::OnDownloadCreated(content::DownloadManager* manager,
@@ -257,8 +257,16 @@ void Session::OnDownloadCreated(content::DownloadManager* manager,
   }
 }
 
+bool Session::IsDestroyed() const {
+  return !browser_context_;
+}
+
+void Session::Destroy() {
+  browser_context_ = nullptr;
+}
+
 void Session::ResolveProxy(const GURL& url, ResolveProxyCallback callback) {
-  new ResolveProxyHelper(browser_context_, url, callback);
+  new ResolveProxyHelper(browser_context(), url, callback);
 }
 
 void Session::ClearCache(const net::CompletionCallback& callback) {
@@ -279,7 +287,7 @@ void Session::ClearStorageData(mate::Arguments* args) {
   }
 
   auto storage_partition =
-      content::BrowserContext::GetStoragePartition(browser_context_, nullptr);
+      content::BrowserContext::GetStoragePartition(browser_context(), nullptr);
   storage_partition->ClearData(
       options.storage_types, options.quota_types, options.origin,
       content::StoragePartition::OriginMatcherFunction(),
@@ -300,7 +308,7 @@ void Session::SetDownloadPath(const base::FilePath& path) {
 
 v8::Local<v8::Value> Session::Cookies(v8::Isolate* isolate) {
   if (cookies_.IsEmpty()) {
-    auto handle = atom::api::Cookies::Create(isolate, browser_context_);
+    auto handle = atom::api::Cookies::Create(isolate, browser_context());
     cookies_.Reset(isolate, handle.ToV8());
   }
   return v8::Local<v8::Value>::New(isolate, cookies_);
@@ -319,8 +327,7 @@ mate::ObjectTemplateBuilder Session::GetObjectTemplateBuilder(
 
 // static
 mate::Handle<Session> Session::CreateFrom(
-    v8::Isolate* isolate,
-    AtomBrowserContext* browser_context) {
+    v8::Isolate* isolate, AtomBrowserContext* browser_context) {
   auto existing = TrackableObject::FromWrappedClass(isolate, browser_context);
   if (existing)
     return mate::CreateHandle(isolate, static_cast<Session*>(existing));
@@ -330,6 +337,14 @@ mate::Handle<Session> Session::CreateFrom(
   return handle;
 }
 
+// static
+mate::Handle<Session> Session::FromPartition(
+    v8::Isolate* isolate, const std::string& partition, bool in_memory) {
+  auto browser_context = brightray::BrowserContext::From(partition, in_memory);
+  return CreateFrom(isolate,
+                    static_cast<AtomBrowserContext*>(browser_context.get()));
+}
+
 void SetWrapSession(const WrapSessionCallback& callback) {
   g_wrap_session = callback;
 }
@@ -348,6 +363,7 @@ void Initialize(v8::Local<v8::Object> exports, v8::Local<v8::Value> unused,
                 v8::Local<v8::Context> context, void* priv) {
   v8::Isolate* isolate = context->GetIsolate();
   mate::Dictionary dict(isolate, exports);
+  dict.SetMethod("fromPartition", &atom::api::Session::FromPartition);
   dict.SetMethod("_setWrapSession", &atom::api::SetWrapSession);
   dict.SetMethod("_clearWrapSession", &atom::api::ClearWrapSession);
 }
diff --git a/atom/browser/api/atom_api_session.h b/atom/browser/api/atom_api_session.h
index c06348974ff..14406e57af5 100644
--- a/atom/browser/api/atom_api_session.h
+++ b/atom/browser/api/atom_api_session.h
@@ -37,7 +37,11 @@ class Session: public mate::TrackableObject<Session>,
   static mate::Handle<Session> CreateFrom(
       v8::Isolate* isolate, AtomBrowserContext* browser_context);
 
-  AtomBrowserContext* browser_context() const { return browser_context_; }
+  // Gets the Session of |partition| and |in_memory|.
+  static mate::Handle<Session> FromPartition(
+      v8::Isolate* isolate, const std::string& partition, bool in_memory);
+
+  AtomBrowserContext* browser_context() const { return browser_context_.get(); }
 
  protected:
   explicit Session(AtomBrowserContext* browser_context);
@@ -47,11 +51,15 @@ class Session: public mate::TrackableObject<Session>,
   void OnDownloadCreated(content::DownloadManager* manager,
                          content::DownloadItem* item) override;
 
-  // mate::Wrappable implementations:
+  // mate::Wrappable:
   mate::ObjectTemplateBuilder GetObjectTemplateBuilder(
       v8::Isolate* isolate) override;
+  bool IsDestroyed() const override;
 
  private:
+  // mate::TrackableObject:
+  void Destroy() override;
+
   void ResolveProxy(const GURL& url, ResolveProxyCallback callback);
   void ClearCache(const net::CompletionCallback& callback);
   void ClearStorageData(mate::Arguments* args);
@@ -59,9 +67,10 @@ class Session: public mate::TrackableObject<Session>,
   void SetDownloadPath(const base::FilePath& path);
   v8::Local<v8::Value> Cookies(v8::Isolate* isolate);
 
+  // Cached object for cookies API.
   v8::Global<v8::Value> cookies_;
 
-  AtomBrowserContext* browser_context_;  // weak ref
+  scoped_refptr<AtomBrowserContext> browser_context_;
 
   DISALLOW_COPY_AND_ASSIGN(Session);
 };
diff --git a/atom/browser/api/atom_api_web_contents.cc b/atom/browser/api/atom_api_web_contents.cc
index 7cefe8e45e3..d22f7aab61f 100644
--- a/atom/browser/api/atom_api_web_contents.cc
+++ b/atom/browser/api/atom_api_web_contents.cc
@@ -11,6 +11,7 @@
 #include "atom/browser/atom_browser_context.h"
 #include "atom/browser/atom_browser_main_parts.h"
 #include "atom/browser/native_window.h"
+#include "atom/browser/web_contents_preferences.h"
 #include "atom/browser/web_view_guest_delegate.h"
 #include "atom/common/api/api_messages.h"
 #include "atom/common/api/event_emitter_caller.h"
@@ -153,31 +154,41 @@ WebContents::WebContents(content::WebContents* web_contents)
   web_contents->SetUserAgentOverride(GetBrowserContext()->GetUserAgent());
 }
 
-WebContents::WebContents(const mate::Dictionary& options) {
+WebContents::WebContents(v8::Isolate* isolate,
+                         const mate::Dictionary& options) {
+  // Whether it is a guest WebContents.
   bool is_guest = false;
   options.Get("isGuest", &is_guest);
-
   type_ = is_guest ? WEB_VIEW : BROWSER_WINDOW;
 
-  content::BrowserContext* browser_context =
-      AtomBrowserMainParts::Get()->browser_context();
+  // Obtain the session.
+  std::string partition;
+  mate::Handle<api::Session> session;
+  if (options.Get("session", &session)) {
+  } else if (options.Get("partition", &partition) && !partition.empty()) {
+    bool in_memory = true;
+    if (base::StartsWith(partition, "persist:", base::CompareCase::SENSITIVE)) {
+      in_memory = false;
+      partition = partition.substr(8);
+    }
+    session = Session::FromPartition(isolate, partition, in_memory);
+  } else {
+    // Use the default session if not specified.
+    session = Session::FromPartition(isolate, "", false);
+  }
+  session_.Reset(isolate, session.ToV8());
+
   content::WebContents* web_contents;
   if (is_guest) {
-    GURL guest_site;
-    options.Get("partition", &guest_site);
-    // use hosts' browser_context when no partition is specified.
-    if (!guest_site.query().empty()) {
-      browser_context = AtomBrowserMainParts::Get()
-          ->GetBrowserContextForPartition(guest_site);
-    }
-    auto site_instance =
-        content::SiteInstance::CreateForURL(browser_context, guest_site);
-    content::WebContents::CreateParams params(browser_context, site_instance);
+    content::SiteInstance* site_instance = content::SiteInstance::CreateForURL(
+        session->browser_context(), GURL("chrome-guest://fake-host"));
+    content::WebContents::CreateParams params(
+        session->browser_context(), site_instance);
     guest_delegate_.reset(new WebViewGuestDelegate);
     params.guest_delegate = guest_delegate_.get();
     web_contents = content::WebContents::Create(params);
   } else {
-    content::WebContents::CreateParams params(browser_context);
+    content::WebContents::CreateParams params(session->browser_context());
     web_contents = content::WebContents::Create(params);
   }
 
@@ -185,6 +196,11 @@ WebContents::WebContents(const mate::Dictionary& options) {
   AttachAsUserData(web_contents);
   InitWithWebContents(web_contents);
 
+  // Save the preferences.
+  base::DictionaryValue web_preferences;
+  mate::ConvertFromV8(isolate, options.GetHandle(), &web_preferences);
+  new WebContentsPreferences(web_contents, &web_preferences);
+
   web_contents->SetUserAgentOverride(GetBrowserContext()->GetUserAgent());
 
   if (is_guest) {
@@ -489,6 +505,7 @@ void WebContents::NavigationEntryCommitted(
 }
 
 void WebContents::Destroy() {
+  session_.Reset();
   if (type_ == WEB_VIEW && managed_web_contents()) {
     // When force destroying the "destroyed" event is not emitted.
     WebContentsDestroyed();
@@ -651,10 +668,6 @@ void WebContents::InspectServiceWorker() {
 }
 
 v8::Local<v8::Value> WebContents::Session(v8::Isolate* isolate) {
-  if (session_.IsEmpty()) {
-    auto handle = Session::CreateFrom(isolate, GetBrowserContext());
-    session_.Reset(isolate, handle.ToV8());
-  }
   return v8::Local<v8::Value>::New(isolate, session_);
 }
 
@@ -890,7 +903,7 @@ mate::Handle<WebContents> WebContents::CreateFrom(
 // static
 mate::Handle<WebContents> WebContents::Create(
     v8::Isolate* isolate, const mate::Dictionary& options) {
-  auto handle =  mate::CreateHandle(isolate, new WebContents(options));
+  auto handle =  mate::CreateHandle(isolate, new WebContents(isolate, options));
   g_wrap_web_contents.Run(handle.ToV8());
   return handle;
 }
diff --git a/atom/browser/api/atom_api_web_contents.h b/atom/browser/api/atom_api_web_contents.h
index e75e88fd703..e2e405b7385 100644
--- a/atom/browser/api/atom_api_web_contents.h
+++ b/atom/browser/api/atom_api_web_contents.h
@@ -48,7 +48,9 @@ class WebContents : public mate::TrackableObject<WebContents>,
   static mate::Handle<WebContents> Create(
       v8::Isolate* isolate, const mate::Dictionary& options);
 
-  void Destroy();
+  // mate::TrackableObject:
+  void Destroy() override;
+
   bool IsAlive() const;
   int GetID() const;
   bool Equal(const WebContents* web_contents) const;
@@ -116,7 +118,7 @@ class WebContents : public mate::TrackableObject<WebContents>,
 
  protected:
   explicit WebContents(content::WebContents* web_contents);
-  explicit WebContents(const mate::Dictionary& options);
+  WebContents(v8::Isolate* isolate, const mate::Dictionary& options);
   ~WebContents();
 
   // mate::Wrappable:
diff --git a/atom/browser/api/atom_api_web_view_manager.cc b/atom/browser/api/atom_api_web_view_manager.cc
index 221d0d7118b..83287ac8b2f 100644
--- a/atom/browser/api/atom_api_web_view_manager.cc
+++ b/atom/browser/api/atom_api_web_view_manager.cc
@@ -3,14 +3,12 @@
 // found in the LICENSE file.
 
 #include "atom/browser/api/atom_api_web_contents.h"
-#include "atom/browser/web_view_constants.h"
+#include "atom/browser/web_contents_preferences.h"
 #include "atom/browser/web_view_manager.h"
-#include "atom/common/native_mate_converters/gurl_converter.h"
+#include "atom/common/native_mate_converters/value_converter.h"
+#include "atom/common/node_includes.h"
 #include "content/public/browser/browser_context.h"
 #include "native_mate/dictionary.h"
-#include "net/base/filename_util.h"
-
-#include "atom/common/node_includes.h"
 
 namespace mate {
 
@@ -26,31 +24,6 @@ struct Converter<content::WebContents*> {
   }
 };
 
-template<>
-struct Converter<atom::WebViewManager::WebViewInfo> {
-  static bool FromV8(v8::Isolate* isolate, v8::Local<v8::Value> val,
-                     atom::WebViewManager::WebViewInfo* out) {
-    Dictionary options;
-    if (!ConvertFromV8(isolate, val, &options))
-      return false;
-
-    GURL preload_url;
-    if (!options.Get(atom::web_view::kPreloadUrl, &preload_url))
-      return false;
-
-    if (!preload_url.is_empty() &&
-        !net::FileURLToFilePath(preload_url, &(out->preload_script)))
-      return false;
-
-    return options.Get(atom::web_view::kNodeIntegration,
-                       &(out->node_integration)) &&
-           options.Get(atom::web_view::kPlugins, &(out->plugins)) &&
-           options.Get(atom::web_view::kPartitionId, &(out->partition_id)) &&
-           options.Get(atom::web_view::kDisableWebSecurity,
-                       &(out->disable_web_security));
-  }
-};
-
 }  // namespace mate
 
 namespace {
@@ -69,17 +42,13 @@ void AddGuest(int guest_instance_id,
               int element_instance_id,
               content::WebContents* embedder,
               content::WebContents* guest_web_contents,
-              atom::WebViewManager::WebViewInfo info) {
+              const base::DictionaryValue& options) {
   auto manager = GetWebViewManager(embedder);
   if (manager)
     manager->AddGuest(guest_instance_id, element_instance_id, embedder,
                       guest_web_contents);
 
-  info.guest_instance_id = guest_instance_id;
-  info.embedder = embedder;
-  auto data = new atom::WebViewManager::WebViewInfoUserData(info);
-  guest_web_contents->SetUserData(
-      atom::web_view::kWebViewInfoKeyName, data);
+  atom::WebContentsPreferences::From(guest_web_contents)->Merge(options);
 }
 
 void RemoveGuest(content::WebContents* embedder, int guest_instance_id) {
diff --git a/atom/browser/api/atom_api_window.cc b/atom/browser/api/atom_api_window.cc
index e6d16fe6fa5..e171fa7698f 100644
--- a/atom/browser/api/atom_api_window.cc
+++ b/atom/browser/api/atom_api_window.cc
@@ -13,6 +13,7 @@
 #include "atom/common/native_mate_converters/gurl_converter.h"
 #include "atom/common/native_mate_converters/image_converter.h"
 #include "atom/common/native_mate_converters/string16_converter.h"
+#include "atom/common/options_switches.h"
 #include "content/public/browser/render_process_host.h"
 #include "native_mate/constructor.h"
 #include "native_mate/dictionary.h"
@@ -64,9 +65,22 @@ void OnCapturePageDone(
 
 
 Window::Window(v8::Isolate* isolate, const mate::Dictionary& options) {
+  // Use options['web-preferences'] to create WebContents.
+  mate::Dictionary web_preferences = mate::Dictionary::CreateEmpty(isolate);
+  options.Get(switches::kWebPreferences, &web_preferences);
+
+  // Be compatible with old options which are now in web_preferences.
+  std::string str;
+  double d;
+  if (options.Get(switches::kNodeIntegration, &str))
+    web_preferences.Set(switches::kNodeIntegration, str);
+  if (options.Get(switches::kPreloadScript, &str))
+    web_preferences.Set(switches::kPreloadScript, str);
+  if (options.Get(switches::kZoomFactor, &d))
+    web_preferences.Set(switches::kZoomFactor, d);
+
   // Creates the WebContents used by BrowserWindow.
-  mate::Dictionary web_contents_options(isolate, v8::Object::New(isolate));
-  auto web_contents = WebContents::Create(isolate, web_contents_options);
+  auto web_contents = WebContents::Create(isolate, web_preferences);
   web_contents_.Reset(isolate, web_contents.ToV8());
   api_web_contents_ = web_contents.get();
 
@@ -207,7 +221,10 @@ bool Window::IsDestroyed() const {
 }
 
 void Window::Destroy() {
-  window_->CloseContents(nullptr);
+  if (window_) {
+    window_->CloseContents(nullptr);
+    window_.reset();
+  }
 }
 
 void Window::Close() {
diff --git a/atom/browser/api/atom_api_window.h b/atom/browser/api/atom_api_window.h
index de2f093ea3e..4384e03a249 100644
--- a/atom/browser/api/atom_api_window.h
+++ b/atom/browser/api/atom_api_window.h
@@ -78,8 +78,10 @@ class Window : public mate::TrackableObject<Window>,
   bool IsDestroyed() const override;
 
  private:
+  // mate::TrackableObject:
+  void Destroy() override;
+
   // APIs for NativeWindow.
-  void Destroy();
   void Close();
   bool IsClosed();
   void Focus();
diff --git a/atom/browser/api/trackable_object.cc b/atom/browser/api/trackable_object.cc
index ae9fa44230a..50bfa59e6a7 100644
--- a/atom/browser/api/trackable_object.cc
+++ b/atom/browser/api/trackable_object.cc
@@ -29,7 +29,9 @@ class IDUserData : public base::SupportsUserData::Data {
 }  // namespace
 
 TrackableObjectBase::TrackableObjectBase()
-    : weak_map_id_(0), wrapped_(nullptr) {
+    : weak_map_id_(0), wrapped_(nullptr), weak_factory_(this) {
+  RegisterDestructionCallback(
+      base::Bind(&TrackableObjectBase::Destroy, weak_factory_.GetWeakPtr()));
 }
 
 TrackableObjectBase::~TrackableObjectBase() {
@@ -61,8 +63,9 @@ int32_t TrackableObjectBase::GetIDFromWrappedClass(base::SupportsUserData* w) {
 }
 
 // static
-void TrackableObjectBase::RegisterDestructionCallback(void (*c)()) {
-  atom::AtomBrowserMainParts::Get()->RegisterDestructionCallback(base::Bind(c));
+void TrackableObjectBase::RegisterDestructionCallback(
+    const base::Closure& closure) {
+  atom::AtomBrowserMainParts::Get()->RegisterDestructionCallback(closure);
 }
 
 }  // namespace mate
diff --git a/atom/browser/api/trackable_object.h b/atom/browser/api/trackable_object.h
index 656904cc45d..8ff7d1c0404 100644
--- a/atom/browser/api/trackable_object.h
+++ b/atom/browser/api/trackable_object.h
@@ -9,7 +9,9 @@
 
 #include "atom/browser/api/event_emitter.h"
 #include "atom/common/id_weak_map.h"
+#include "base/bind.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 
 namespace base {
 class SupportsUserData;
@@ -28,6 +30,9 @@ class TrackableObjectBase : public mate::EventEmitter {
   // Wrap TrackableObject into a class that SupportsUserData.
   void AttachAsUserData(base::SupportsUserData* wrapped);
 
+  // Subclasses should implement this to destroy their native types.
+  virtual void Destroy() = 0;
+
  protected:
   ~TrackableObjectBase() override;
 
@@ -39,12 +44,14 @@ class TrackableObjectBase : public mate::EventEmitter {
 
   // Register a callback that should be destroyed before JavaScript environment
   // gets destroyed.
-  static void RegisterDestructionCallback(void (*callback)());
+  static void RegisterDestructionCallback(const base::Closure& closure);
 
   int32_t weak_map_id_;
   base::SupportsUserData* wrapped_;
 
  private:
+  base::WeakPtrFactory<TrackableObjectBase> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(TrackableObjectBase);
 };
 
@@ -85,7 +92,8 @@ class TrackableObject : public TrackableObjectBase {
   }
 
   TrackableObject() {
-    RegisterDestructionCallback(&TrackableObject<T>::ReleaseAllWeakReferences);
+    RegisterDestructionCallback(
+        base::Bind(&TrackableObject<T>::ReleaseAllWeakReferences));
   }
 
   // Removes this instance from the weak map.
diff --git a/atom/browser/atom_browser_client.cc b/atom/browser/atom_browser_client.cc
index fad952d5336..e45caceab01 100644
--- a/atom/browser/atom_browser_client.cc
+++ b/atom/browser/atom_browser_client.cc
@@ -15,8 +15,7 @@
 #include "atom/browser/atom_speech_recognition_manager_delegate.h"
 #include "atom/browser/browser.h"
 #include "atom/browser/native_window.h"
-#include "atom/browser/web_view_manager.h"
-#include "atom/browser/web_view_constants.h"
+#include "atom/browser/web_contents_preferences.h"
 #include "atom/browser/window_list.h"
 #include "atom/common/options_switches.h"
 #include "base/command_line.h"
@@ -38,6 +37,7 @@
 #include "net/ssl/ssl_cert_request_info.h"
 #include "ppapi/host/ppapi_host.h"
 #include "ui/base/l10n/l10n_util.h"
+#include "v8/include/v8.h"
 
 namespace atom {
 
@@ -54,37 +54,6 @@ bool g_suppress_renderer_process_restart = false;
 // Custom schemes to be registered to standard.
 std::string g_custom_schemes = "";
 
-// Find out the owner of the child process according to |process_id|.
-enum ProcessOwner {
-  OWNER_NATIVE_WINDOW,
-  OWNER_GUEST_WEB_CONTENTS,
-  OWNER_NONE,  // it might be devtools though.
-};
-
-ProcessOwner GetProcessOwner(int process_id,
-                             NativeWindow** window,
-                             WebViewManager::WebViewInfo* info) {
-  content::WebContents* web_contents = content::WebContents::FromRenderViewHost(
-      content::RenderViewHost::FromID(process_id, kDefaultRoutingID));
-  if (!web_contents)
-    return OWNER_NONE;
-
-  // First search for NativeWindow.
-  *window = NativeWindow::FromWebContents(web_contents);
-  if (*window)
-    return OWNER_NATIVE_WINDOW;
-
-  // Then search for guest WebContents.
-  auto data = static_cast<WebViewManager::WebViewInfoUserData*>(
-      web_contents->GetUserData(web_view::kWebViewInfoKeyName));
-  if (data) {
-    *info = data->web_view_info();
-    return OWNER_GUEST_WEB_CONTENTS;
-  }
-
-  return OWNER_NONE;
-}
-
 scoped_refptr<net::X509Certificate> ImportCertFromFile(
     const base::FilePath& path) {
   if (path.empty())
@@ -160,16 +129,7 @@ void AtomBrowserClient::OverrideWebkitPrefs(
 
   // Custom preferences of guest page.
   auto web_contents = content::WebContents::FromRenderViewHost(host);
-  auto info = static_cast<WebViewManager::WebViewInfoUserData*>(
-      web_contents->GetUserData(web_view::kWebViewInfoKeyName));
-  if (info) {
-    prefs->web_security_enabled = !info->web_view_info().disable_web_security;
-    return;
-  }
-
-  NativeWindow* window = NativeWindow::FromWebContents(web_contents);
-  if (window)
-    window->OverrideWebkitPrefs(prefs);
+  WebContentsPreferences::OverrideWebkitPrefs(web_contents, prefs);
 }
 
 std::string AtomBrowserClient::GetApplicationLocale() {
@@ -225,23 +185,14 @@ void AtomBrowserClient::AppendExtraCommandLineSwitches(
   if (ContainsKey(pending_processes_, process_id))
     process_id = pending_processes_[process_id];
 
-  NativeWindow* window;
-  WebViewManager::WebViewInfo info;
-  ProcessOwner owner = GetProcessOwner(process_id, &window, &info);
+  // Get the WebContents of the render process.
+  content::WebContents* web_contents = content::WebContents::FromRenderViewHost(
+      content::RenderViewHost::FromID(process_id, kDefaultRoutingID));
+  if (!web_contents)
+    return;
 
-  if (owner == OWNER_NATIVE_WINDOW) {
-    window->AppendExtraCommandLineSwitches(command_line);
-  } else if (owner == OWNER_GUEST_WEB_CONTENTS) {
-    command_line->AppendSwitchASCII(
-        switches::kGuestInstanceID, base::IntToString(info.guest_instance_id));
-    command_line->AppendSwitchASCII(
-        switches::kNodeIntegration, info.node_integration ? "true" : "false");
-    if (info.plugins)
-      command_line->AppendSwitch(switches::kEnablePlugins);
-    if (!info.preload_script.empty())
-      command_line->AppendSwitchPath(
-          switches::kPreloadScript, info.preload_script);
-  }
+  WebContentsPreferences::AppendExtraCommandLineSwitches(
+      web_contents, command_line);
 }
 
 void AtomBrowserClient::DidCreatePpapiPlugin(
diff --git a/atom/browser/atom_browser_context.cc b/atom/browser/atom_browser_context.cc
index 583a6324a8f..d1ef09e70ff 100644
--- a/atom/browser/atom_browser_context.cc
+++ b/atom/browser/atom_browser_context.cc
@@ -56,8 +56,10 @@ std::string RemoveWhitespace(const std::string& str) {
 
 }  // namespace
 
-AtomBrowserContext::AtomBrowserContext()
-    : job_factory_(new AtomURLRequestJobFactory) {
+AtomBrowserContext::AtomBrowserContext(const std::string& partition,
+                                       bool in_memory)
+    : brightray::BrowserContext(partition, in_memory),
+      job_factory_(new AtomURLRequestJobFactory) {
 }
 
 AtomBrowserContext::~AtomBrowserContext() {
@@ -150,7 +152,7 @@ AtomBrowserContext::GetDownloadManagerDelegate() {
 
 content::BrowserPluginGuestManager* AtomBrowserContext::GetGuestManager() {
   if (!guest_manager_)
-    guest_manager_.reset(new WebViewManager(this));
+    guest_manager_.reset(new WebViewManager);
   return guest_manager_.get();
 }
 
@@ -162,3 +164,13 @@ void AtomBrowserContext::RegisterPrefs(PrefRegistrySimple* pref_registry) {
 }
 
 }  // namespace atom
+
+namespace brightray {
+
+// static
+scoped_refptr<BrowserContext> BrowserContext::Create(
+    const std::string& partition, bool in_memory) {
+  return make_scoped_refptr(new atom::AtomBrowserContext(partition, in_memory));
+}
+
+}  // namespace brightray
diff --git a/atom/browser/atom_browser_context.h b/atom/browser/atom_browser_context.h
index c1ff613b8c0..c99461ad9a8 100644
--- a/atom/browser/atom_browser_context.h
+++ b/atom/browser/atom_browser_context.h
@@ -17,8 +17,8 @@ class WebViewManager;
 
 class AtomBrowserContext : public brightray::BrowserContext {
  public:
-  AtomBrowserContext();
-  virtual ~AtomBrowserContext();
+  AtomBrowserContext(const std::string& partition, bool in_memory);
+  ~AtomBrowserContext() override;
 
   // brightray::URLRequestContextGetter::Delegate:
   std::string GetUserAgent() override;
@@ -41,7 +41,8 @@ class AtomBrowserContext : public brightray::BrowserContext {
   scoped_ptr<AtomDownloadManagerDelegate> download_manager_delegate_;
   scoped_ptr<WebViewManager> guest_manager_;
 
-  AtomURLRequestJobFactory* job_factory_;  // Weak reference.
+  // Managed by brightray::BrowserContext.
+  AtomURLRequestJobFactory* job_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AtomBrowserContext);
 };
diff --git a/atom/browser/atom_browser_main_parts.cc b/atom/browser/atom_browser_main_parts.cc
index 806c12b7eac..31a49046414 100644
--- a/atom/browser/atom_browser_main_parts.cc
+++ b/atom/browser/atom_browser_main_parts.cc
@@ -26,24 +26,6 @@
 
 namespace atom {
 
-namespace {
-
-const base::FilePath::CharType kStoragePartitionDirname[] =
-    FILE_PATH_LITERAL("Partitions");
-
-void GetStoragePartitionConfig(const GURL& partition,
-                               base::FilePath* partition_path,
-                               bool* in_memory,
-                               std::string* id) {
-  *in_memory = (partition.path() != "/persist");
-  net::UnescapeRule::Type flags =
-      net::UnescapeRule::SPACES | net::UnescapeRule::URL_SPECIAL_CHARS;
-  *id = net::UnescapeURLComponent(partition.query(), flags);
-  *partition_path = base::FilePath(kStoragePartitionDirname).AppendASCII(*id);
-}
-
-}  // namespace
-
 // static
 AtomBrowserMainParts* AtomBrowserMainParts::self_ = NULL;
 
@@ -68,30 +50,11 @@ AtomBrowserMainParts* AtomBrowserMainParts::Get() {
   return self_;
 }
 
-content::BrowserContext* AtomBrowserMainParts::GetBrowserContextForPartition(
-    const GURL& partition) {
-  std::string id;
-  bool in_memory;
-  base::FilePath partition_path;
-  GetStoragePartitionConfig(partition, &partition_path, &in_memory, &id);
-  if (browser_context_map_.contains(id))
-    return browser_context_map_.get(id);
-
-  scoped_ptr<brightray::BrowserContext> browser_context(CreateBrowserContext());
-  browser_context->Initialize(partition_path.AsUTF8Unsafe(), in_memory);
-  browser_context_map_.set(id, browser_context.Pass());
-  return browser_context_map_.get(id);
-}
-
 void AtomBrowserMainParts::RegisterDestructionCallback(
     const base::Closure& callback) {
   destruction_callbacks_.push_back(callback);
 }
 
-brightray::BrowserContext* AtomBrowserMainParts::CreateBrowserContext() {
-  return new AtomBrowserContext();
-}
-
 void AtomBrowserMainParts::PostEarlyInitialization() {
   brightray::BrowserMainParts::PostEarlyInitialization();
 
diff --git a/atom/browser/atom_browser_main_parts.h b/atom/browser/atom_browser_main_parts.h
index d952f432882..59ff7c977c8 100644
--- a/atom/browser/atom_browser_main_parts.h
+++ b/atom/browser/atom_browser_main_parts.h
@@ -6,11 +6,9 @@
 #define ATOM_BROWSER_ATOM_BROWSER_MAIN_PARTS_H_
 
 #include <list>
-#include <map>
 #include <string>
 
 #include "base/callback.h"
-#include "base/containers/scoped_ptr_hash_map.h"
 #include "base/timer/timer.h"
 #include "brightray/browser/browser_main_parts.h"
 #include "content/public/browser/browser_context.h"
@@ -33,10 +31,6 @@ class AtomBrowserMainParts : public brightray::BrowserMainParts {
 
   static AtomBrowserMainParts* Get();
 
-  // Returns the BrowserContext associated with the partition.
-  content::BrowserContext* GetBrowserContextForPartition(
-      const GURL& partition);
-
   // Register a callback that should be destroyed before JavaScript environment
   // gets destroyed.
   void RegisterDestructionCallback(const base::Closure& callback);
@@ -44,10 +38,7 @@ class AtomBrowserMainParts : public brightray::BrowserMainParts {
   Browser* browser() { return browser_.get(); }
 
  protected:
-  // Implementations of brightray::BrowserMainParts.
-  brightray::BrowserContext* CreateBrowserContext() override;
-
-  // Implementations of content::BrowserMainParts.
+  // content::BrowserMainParts:
   void PostEarlyInitialization() override;
   void PreMainMessageLoopRun() override;
 #if defined(OS_MACOSX)
@@ -78,10 +69,6 @@ class AtomBrowserMainParts : public brightray::BrowserMainParts {
   // List of callbacks should be executed before destroying JS env.
   std::list<base::Closure> destruction_callbacks_;
 
-  // partition_id => browser_context
-  base::ScopedPtrHashMap<std::string, scoped_ptr<brightray::BrowserContext>>
-      browser_context_map_;
-
   static AtomBrowserMainParts* self_;
 
   DISALLOW_COPY_AND_ASSIGN(AtomBrowserMainParts);
diff --git a/atom/browser/lib/guest-view-manager.coffee b/atom/browser/lib/guest-view-manager.coffee
index 58127469908..1c05b65b2dc 100644
--- a/atom/browser/lib/guest-view-manager.coffee
+++ b/atom/browser/lib/guest-view-manager.coffee
@@ -38,29 +38,12 @@ moveLastToFirst = (list) ->
 getNextInstanceId = (webContents) ->
   ++nextInstanceId
 
-# Generate URL encoded partition id.
-getPartitionId = (partition) ->
-  # Guest site url will be chrome-guest://fake-host/{persist}?{partitionId}
-  partitionId = "chrome-guest://fake-host/"
-  if partition
-    persist = partition.startsWith('persist:')
-    if persist
-      partition = partition.substring('persist:'.length)
-      partitionId += 'persist?'
-    else
-      # Just to differentiate from same persistant ID
-      partition += "_temp"
-      partitionId += '?'
-    partitionId += encodeURIComponent(partition)
-  return partitionId
-
 # Create a new guest instance.
 createGuest = (embedder, params) ->
   webViewManager ?= process.atomBinding 'web_view_manager'
 
   id = getNextInstanceId embedder
-  partitionId = getPartitionId params.partition
-  guest = webContents.create {isGuest: true, partition: partitionId, embedder}
+  guest = webContents.create {isGuest: true, partition: params.partition, embedder}
   guestInstances[id] = {guest, embedder}
 
   # Destroy guest when the embedder is gone or navigated.
@@ -132,12 +115,13 @@ attachGuest = (embedder, elementInstanceId, guestInstanceId, params) ->
     return unless guestInstances[oldGuestInstanceId]?
     destroyGuest embedder, oldGuestInstanceId
 
-  webViewManager.addGuest guestInstanceId, elementInstanceId, embedder, guest,
-    nodeIntegration: params.nodeintegration
-    plugins: params.plugins
-    disableWebSecurity: params.disablewebsecurity
-    preloadUrl: params.preload ? ''
-    partitionId: getPartitionId(params.partition)
+  webPreferences =
+    'guest-instance-id': guestInstanceId
+    'node-integration': params.nodeintegration ? false
+    'plugins': params.plugins
+    'web-security': !params.disablewebsecurity
+  webPreferences['preload-url'] = params.preload if params.preload
+  webViewManager.addGuest guestInstanceId, elementInstanceId, embedder, guest, webPreferences
 
   guest.attachParams = params
   embedderElementsMap[key] = guestInstanceId
diff --git a/atom/browser/native_window.cc b/atom/browser/native_window.cc
index 96085846bca..997fe72c4ae 100644
--- a/atom/browser/native_window.cc
+++ b/atom/browser/native_window.cc
@@ -15,12 +15,10 @@
 #include "atom/common/native_mate_converters/image_converter.h"
 #include "atom/common/native_mate_converters/file_path_converter.h"
 #include "atom/common/options_switches.h"
-#include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/json/json_writer.h"
 #include "base/prefs/pref_service.h"
 #include "base/message_loop/message_loop.h"
-#include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "brightray/browser/inspectable_web_contents.h"
 #include "brightray/browser/inspectable_web_contents_view.h"
@@ -31,8 +29,6 @@
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/common/content_switches.h"
-#include "content/public/common/renderer_preferences.h"
-#include "content/public/common/web_preferences.h"
 #include "ipc/ipc_message_macros.h"
 #include "native_mate/dictionary.h"
 #include "ui/gfx/codec/png_codec.h"
@@ -43,10 +39,6 @@
 #include "ui/gfx/screen.h"
 #include "ui/gl/gpu_switching_manager.h"
 
-#if defined(OS_WIN)
-#include "ui/gfx/switches.h"
-#endif
-
 using content::NavigationEntry;
 using content::RenderWidgetHostView;
 using content::RenderWidgetHost;
@@ -57,17 +49,6 @@ namespace atom {
 
 namespace {
 
-// Array of available web runtime features.
-const char* kWebRuntimeFeatures[] = {
-  switches::kExperimentalFeatures,
-  switches::kExperimentalCanvasFeatures,
-  switches::kSubpixelFontScaling,
-  switches::kOverlayScrollbars,
-  switches::kOverlayFullscreenVideo,
-  switches::kSharedWorker,
-  switches::kPageVisibility,
-};
-
 // Convert draggable regions in raw format to SkRegion format. Caller is
 // responsible for deleting the returned SkRegion instance.
 scoped_ptr<SkRegion> DraggableRegionsToSkRegion(
@@ -94,9 +75,7 @@ NativeWindow::NativeWindow(
       transparent_(false),
       enable_larger_than_screen_(false),
       is_closed_(false),
-      node_integration_(true),
       has_dialog_attached_(false),
-      zoom_factor_(1.0),
       aspect_ratio_(0.0),
       inspectable_web_contents_(inspectable_web_contents),
       weak_factory_(this) {
@@ -105,7 +84,6 @@ NativeWindow::NativeWindow(
   options.Get(switches::kFrame, &has_frame_);
   options.Get(switches::kTransparent, &transparent_);
   options.Get(switches::kEnableLargerThanScreen, &enable_larger_than_screen_);
-  options.Get(switches::kNodeIntegration, &node_integration_);
 
   // Tell the content module to initialize renderer widget with transparent
   // mode.
@@ -114,25 +92,6 @@ NativeWindow::NativeWindow(
   // Read icon before window is created.
   options.Get(switches::kIcon, &icon_);
 
-  // The "preload" option must be absolute path.
-  if (options.Get(switches::kPreloadScript, &preload_script_) &&
-      !preload_script_.IsAbsolute()) {
-    LOG(ERROR) << "Path of \"preload\" script must be absolute.";
-    preload_script_.clear();
-  }
-
-  // Be compatible with old API of "node-integration" option.
-  std::string old_string_token;
-  if (options.Get(switches::kNodeIntegration, &old_string_token) &&
-      old_string_token != "disable")
-    node_integration_ = true;
-
-  // Read the web preferences.
-  options.Get(switches::kWebPreferences, &web_preferences_);
-
-  // Read the zoom factor before any navigation.
-  options.Get(switches::kZoomFactor, &zoom_factor_);
-
   WindowList::AddWindow(this);
 }
 
@@ -381,81 +340,6 @@ void NativeWindow::RendererResponsive(content::WebContents* source) {
   FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnRendererResponsive());
 }
 
-void NativeWindow::AppendExtraCommandLineSwitches(
-    base::CommandLine* command_line) {
-  // Append --node-integration to renderer process.
-  command_line->AppendSwitchASCII(switches::kNodeIntegration,
-                                  node_integration_ ? "true" : "false");
-
-  // Append --preload.
-  if (!preload_script_.empty())
-    command_line->AppendSwitchPath(switches::kPreloadScript, preload_script_);
-
-  // Append --zoom-factor.
-  if (zoom_factor_ != 1.0)
-    command_line->AppendSwitchASCII(switches::kZoomFactor,
-                                    base::DoubleToString(zoom_factor_));
-
-  if (web_preferences_.IsEmpty())
-    return;
-
-  bool b;
-#if defined(OS_WIN)
-  // Check if DirectWrite is disabled.
-  if (web_preferences_.Get(switches::kDirectWrite, &b) && !b)
-    command_line->AppendSwitch(::switches::kDisableDirectWrite);
-#endif
-
-  // Check if plugins are enabled.
-  if (web_preferences_.Get("plugins", &b) && b)
-    command_line->AppendSwitch(switches::kEnablePlugins);
-
-  // This set of options are not availabe in WebPreferences, so we have to pass
-  // them via command line and enable them in renderer procss.
-  for (size_t i = 0; i < arraysize(kWebRuntimeFeatures); ++i) {
-    const char* feature = kWebRuntimeFeatures[i];
-    if (web_preferences_.Get(feature, &b))
-      command_line->AppendSwitchASCII(feature, b ? "true" : "false");
-  }
-}
-
-void NativeWindow::OverrideWebkitPrefs(content::WebPreferences* prefs) {
-  if (web_preferences_.IsEmpty())
-    return;
-
-  bool b;
-  std::vector<base::FilePath> list;
-  if (web_preferences_.Get("javascript", &b))
-    prefs->javascript_enabled = b;
-  if (web_preferences_.Get("images", &b))
-    prefs->images_enabled = b;
-  if (web_preferences_.Get("java", &b))
-    prefs->java_enabled = b;
-  if (web_preferences_.Get("text-areas-are-resizable", &b))
-    prefs->text_areas_are_resizable = b;
-  if (web_preferences_.Get("webgl", &b))
-    prefs->experimental_webgl_enabled = b;
-  if (web_preferences_.Get("webaudio", &b))
-    prefs->webaudio_enabled = b;
-  if (web_preferences_.Get("web-security", &b)) {
-    prefs->web_security_enabled = b;
-    prefs->allow_displaying_insecure_content = !b;
-    prefs->allow_running_insecure_content = !b;
-  }
-  if (web_preferences_.Get("allow-displaying-insecure-content", &b))
-    prefs->allow_displaying_insecure_content = b;
-  if (web_preferences_.Get("allow-running-insecure-content", &b))
-    prefs->allow_running_insecure_content = b;
-  if (web_preferences_.Get("extra-plugin-dirs", &list)) {
-    if (content::PluginService::GetInstance()->NPAPIPluginsSupported()) {
-      for (size_t i = 0; i < list.size(); ++i)
-        content::PluginService::GetInstance()->AddExtraPluginDir(list[i]);
-    } else {
-      LOG(WARNING) << "NPAPI plugins not supported on this platform";
-    }
-  }
-}
-
 void NativeWindow::NotifyWindowClosed() {
   if (is_closed_)
     return;
diff --git a/atom/browser/native_window.h b/atom/browser/native_window.h
index 10889a5ccaf..b89e2b58e6e 100644
--- a/atom/browser/native_window.h
+++ b/atom/browser/native_window.h
@@ -19,23 +19,17 @@
 #include "content/public/browser/readback_types.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
-#include "native_mate/persistent_dictionary.h"
 #include "ui/gfx/image/image.h"
 #include "ui/gfx/image/image_skia.h"
 
 class SkRegion;
 
-namespace base {
-class CommandLine;
-}
-
 namespace brightray {
 class InspectableWebContents;
 }
 
 namespace content {
 struct NativeWebKeyboardEvent;
-struct WebPreferences;
 }
 
 namespace gfx {
@@ -189,10 +183,6 @@ class NativeWindow : public content::WebContentsObserver,
       content::WebContents*,
       const content::NativeWebKeyboardEvent& event) {}
 
-  // Called when renderer process is going to be started.
-  void AppendExtraCommandLineSwitches(base::CommandLine* command_line);
-  void OverrideWebkitPrefs(content::WebPreferences* prefs);
-
   // Public API used by platform-dependent delegates and observers to send UI
   // related notifications.
   void NotifyWindowClosed();
@@ -282,9 +272,6 @@ class NativeWindow : public content::WebContentsObserver,
   // The windows has been closed.
   bool is_closed_;
 
-  // Whether node integration is enabled.
-  bool node_integration_;
-
   // There is a dialog that has been attached to window.
   bool has_dialog_attached_;
 
@@ -292,15 +279,6 @@ class NativeWindow : public content::WebContentsObserver,
   // it should be cancelled when we can prove that the window is responsive.
   base::CancelableClosure window_unresposive_closure_;
 
-  // Web preferences.
-  mate::PersistentDictionary web_preferences_;
-
-  // The script to load before page's JavaScript starts to run.
-  base::FilePath preload_script_;
-
-  // Page's default zoom factor.
-  double zoom_factor_;
-
   // Used to maintain the aspect ratio of a view which is inside of the
   // content view.
   double aspect_ratio_;
diff --git a/atom/browser/web_contents_preferences.cc b/atom/browser/web_contents_preferences.cc
new file mode 100644
index 00000000000..19ea826a5ff
--- /dev/null
+++ b/atom/browser/web_contents_preferences.cc
@@ -0,0 +1,162 @@
+// Copyright (c) 2015 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "atom/browser/web_contents_preferences.h"
+
+#include <string>
+
+#include "atom/common/options_switches.h"
+#include "base/command_line.h"
+#include "base/strings/string_number_conversions.h"
+#include "content/public/common/web_preferences.h"
+#include "net/base/filename_util.h"
+
+#if defined(OS_WIN)
+#include "ui/gfx/switches.h"
+#endif
+
+namespace atom {
+
+namespace {
+
+// Pointer as WebContents's user data key.
+const char* kWebPreferencesKey = "WebContentsPreferences";
+
+// Array of available web runtime features.
+const char* kWebRuntimeFeatures[] = {
+  switches::kExperimentalFeatures,
+  switches::kExperimentalCanvasFeatures,
+  switches::kSubpixelFontScaling,
+  switches::kOverlayScrollbars,
+  switches::kOverlayFullscreenVideo,
+  switches::kSharedWorker,
+  switches::kPageVisibility,
+};
+
+}  // namespace
+
+WebContentsPreferences::WebContentsPreferences(
+    content::WebContents* web_contents,
+    base::DictionaryValue* web_preferences) {
+  web_preferences_.Swap(web_preferences);
+  web_contents->SetUserData(kWebPreferencesKey, this);
+}
+
+WebContentsPreferences::~WebContentsPreferences() {
+}
+
+void WebContentsPreferences::Merge(const base::DictionaryValue& extend) {
+  web_preferences_.MergeDictionary(&extend);
+}
+
+// static
+WebContentsPreferences* WebContentsPreferences::From(
+    content::WebContents* web_contents) {
+  return static_cast<WebContentsPreferences*>(
+      web_contents->GetUserData(kWebPreferencesKey));
+}
+
+// static
+void WebContentsPreferences::AppendExtraCommandLineSwitches(
+    content::WebContents* web_contents, base::CommandLine* command_line) {
+  WebContentsPreferences* self = From(web_contents);
+  if (!self)
+    return;
+
+  base::DictionaryValue& web_preferences = self->web_preferences_;
+
+  bool b;
+#if defined(OS_WIN)
+  // Check if DirectWrite is disabled.
+  if (web_preferences.GetBoolean(switches::kDirectWrite, &b) && !b)
+    command_line->AppendSwitch(::switches::kDisableDirectWrite);
+#endif
+
+  // Check if plugins are enabled.
+  if (web_preferences.GetBoolean("plugins", &b) && b)
+    command_line->AppendSwitch(switches::kEnablePlugins);
+
+  // This set of options are not availabe in WebPreferences, so we have to pass
+  // them via command line and enable them in renderer procss.
+  for (size_t i = 0; i < arraysize(kWebRuntimeFeatures); ++i) {
+    const char* feature = kWebRuntimeFeatures[i];
+    if (web_preferences.GetBoolean(feature, &b))
+      command_line->AppendSwitchASCII(feature, b ? "true" : "false");
+  }
+
+  // Check if we have node integration specified.
+  bool node_integration = true;
+  web_preferences.GetBoolean(switches::kNodeIntegration, &node_integration);
+  // Be compatible with old API of "node-integration" option.
+  std::string old_token;
+  if (web_preferences.GetString(switches::kNodeIntegration, &old_token) &&
+      old_token != "disable")
+    node_integration = true;
+  command_line->AppendSwitchASCII(switches::kNodeIntegration,
+                                  node_integration ? "true" : "false");
+
+  // The preload script.
+  base::FilePath::StringType preload;
+  if (web_preferences.GetString(switches::kPreloadScript, &preload)) {
+    if (base::FilePath(preload).IsAbsolute())
+      command_line->AppendSwitchNative(switches::kPreloadScript, preload);
+    else
+      LOG(ERROR) << "preload script must have abosulute path.";
+  } else if (web_preferences.GetString(switches::kPreloadUrl, &preload)) {
+    // Translate to file path if there is "preload-url" option.
+    base::FilePath preload_path;
+    if (net::FileURLToFilePath(GURL(preload), &preload_path))
+      command_line->AppendSwitchPath(switches::kPreloadScript, preload_path);
+    else
+      LOG(ERROR) << "preload url must be file:// protocol.";
+  }
+
+  // The zoom factor.
+  double zoom_factor = 1.0;
+  if (web_preferences.GetDouble(switches::kZoomFactor, &zoom_factor) &&
+      zoom_factor != 1.0)
+    command_line->AppendSwitchASCII(switches::kZoomFactor,
+                                    base::DoubleToString(zoom_factor));
+
+  // --guest-instance-id, which is used to identify guest WebContents.
+  int guest_instance_id;
+  if (web_preferences.GetInteger(switches::kGuestInstanceID,
+                                 &guest_instance_id))
+      command_line->AppendSwitchASCII(switches::kGuestInstanceID,
+                                      base::IntToString(guest_instance_id));
+}
+
+// static
+void WebContentsPreferences::OverrideWebkitPrefs(
+    content::WebContents* web_contents, content::WebPreferences* prefs) {
+  WebContentsPreferences* self = From(web_contents);
+  if (!self)
+    return;
+
+  bool b;
+  if (self->web_preferences_.GetBoolean("javascript", &b))
+    prefs->javascript_enabled = b;
+  if (self->web_preferences_.GetBoolean("images", &b))
+    prefs->images_enabled = b;
+  if (self->web_preferences_.GetBoolean("java", &b))
+    prefs->java_enabled = b;
+  if (self->web_preferences_.GetBoolean("text-areas-are-resizable", &b))
+    prefs->text_areas_are_resizable = b;
+  if (self->web_preferences_.GetBoolean("webgl", &b))
+    prefs->experimental_webgl_enabled = b;
+  if (self->web_preferences_.GetBoolean("webaudio", &b))
+    prefs->webaudio_enabled = b;
+  if (self->web_preferences_.GetBoolean("web-security", &b)) {
+    prefs->web_security_enabled = b;
+    prefs->allow_displaying_insecure_content = !b;
+    prefs->allow_running_insecure_content = !b;
+  }
+  if (self->web_preferences_.GetBoolean("allow-displaying-insecure-content",
+                                        &b))
+    prefs->allow_displaying_insecure_content = b;
+  if (self->web_preferences_.GetBoolean("allow-running-insecure-content", &b))
+    prefs->allow_running_insecure_content = b;
+}
+
+}  // namespace atom
diff --git a/atom/browser/web_contents_preferences.h b/atom/browser/web_contents_preferences.h
new file mode 100644
index 00000000000..310456725aa
--- /dev/null
+++ b/atom/browser/web_contents_preferences.h
@@ -0,0 +1,53 @@
+// Copyright (c) 2015 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ATOM_BROWSER_WEB_CONTENTS_PREFERENCES_H_
+#define ATOM_BROWSER_WEB_CONTENTS_PREFERENCES_H_
+
+#include "base/values.h"
+#include "content/public/browser/web_contents_user_data.h"
+
+namespace base {
+class CommandLine;
+}
+
+namespace content {
+struct WebPreferences;
+}
+
+namespace atom {
+
+// Stores and applies the preferences of WebContents.
+class WebContentsPreferences
+    : public content::WebContentsUserData<WebContentsPreferences> {
+ public:
+  // Get the preferences of |web_contents|.
+  static WebContentsPreferences* From(content::WebContents* web_contents);
+
+  // Append command paramters according to |web_contents|'s preferences.
+  static void AppendExtraCommandLineSwitches(
+      content::WebContents* web_contents, base::CommandLine* command_line);
+
+  // Modify the WebPreferences according to |web_contents|'s preferences.
+  static void OverrideWebkitPrefs(
+      content::WebContents* web_contents, content::WebPreferences* prefs);
+
+  WebContentsPreferences(content::WebContents* web_contents,
+                         base::DictionaryValue* web_preferences);
+  ~WebContentsPreferences() override;
+
+  // $.extend(|web_preferences_|, |new_web_preferences|).
+  void Merge(const base::DictionaryValue& new_web_preferences);
+
+ private:
+  friend class content::WebContentsUserData<WebContentsPreferences>;
+
+  base::DictionaryValue web_preferences_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebContentsPreferences);
+};
+
+}  // namespace atom
+
+#endif  // ATOM_BROWSER_WEB_CONTENTS_PREFERENCES_H_
diff --git a/atom/browser/web_view_manager.cc b/atom/browser/web_view_manager.cc
index 9d0b9337599..d404c1a4368 100644
--- a/atom/browser/web_view_manager.cc
+++ b/atom/browser/web_view_manager.cc
@@ -5,13 +5,12 @@
 #include "atom/browser/web_view_manager.h"
 
 #include "atom/browser/atom_browser_context.h"
-#include "atom/browser/atom_browser_main_parts.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/web_contents.h"
 
 namespace atom {
 
-WebViewManager::WebViewManager(content::BrowserContext* context) {
+WebViewManager::WebViewManager() {
 }
 
 WebViewManager::~WebViewManager() {
@@ -21,7 +20,6 @@ void WebViewManager::AddGuest(int guest_instance_id,
                               int element_instance_id,
                               content::WebContents* embedder,
                               content::WebContents* web_contents) {
-  base::AutoLock auto_lock(lock_);
   web_contents_embedder_map_[guest_instance_id] = { web_contents, embedder };
 
   // Map the element in embedder to guest.
@@ -31,7 +29,6 @@ void WebViewManager::AddGuest(int guest_instance_id,
 }
 
 void WebViewManager::RemoveGuest(int guest_instance_id) {
-  base::AutoLock auto_lock(lock_);
   if (!ContainsKey(web_contents_embedder_map_, guest_instance_id))
     return;
 
diff --git a/atom/browser/web_view_manager.h b/atom/browser/web_view_manager.h
index 20c04484972..ff9a8ecba2a 100644
--- a/atom/browser/web_view_manager.h
+++ b/atom/browser/web_view_manager.h
@@ -7,45 +7,14 @@
 
 #include <map>
 
-#include "base/files/file_path.h"
-#include "base/supports_user_data.h"
-#include "base/synchronization/lock.h"
 #include "content/public/browser/browser_plugin_guest_manager.h"
-#include "content/public/browser/site_instance.h"
-
-namespace content {
-class BrowserContext;
-class RenderProcessHost;
-}
 
 namespace atom {
 
 class WebViewManager : public content::BrowserPluginGuestManager {
  public:
-  struct WebViewInfo {
-    int guest_instance_id;
-    content::WebContents* embedder;
-    bool node_integration;
-    bool plugins;
-    bool disable_web_security;
-    base::FilePath preload_script;
-    GURL partition_id;
-  };
-
-  class WebViewInfoUserData : public base::SupportsUserData::Data {
-   public:
-    explicit WebViewInfoUserData(WebViewInfo info)
-        : web_view_info_(info) {}
-    ~WebViewInfoUserData() override {}
-
-    WebViewInfo& web_view_info() { return web_view_info_; }
-
-   private:
-    WebViewInfo web_view_info_;
-  };
-
-  explicit WebViewManager(content::BrowserContext* context);
-  virtual ~WebViewManager();
+  WebViewManager();
+  ~WebViewManager() override;
 
   void AddGuest(int guest_instance_id,
                 int element_instance_id,
@@ -90,8 +59,6 @@ class WebViewManager : public content::BrowserPluginGuestManager {
   // (embedder_process_id, element_instance_id) => guest_instance_id
   std::map<ElementInstanceKey, int> element_instance_id_to_guest_map_;
 
-  base::Lock lock_;
-
   DISALLOW_COPY_AND_ASSIGN(WebViewManager);
 };
 
diff --git a/atom/common/options_switches.cc b/atom/common/options_switches.cc
index 8f457116ec3..ce5398e447f 100644
--- a/atom/common/options_switches.cc
+++ b/atom/common/options_switches.cc
@@ -75,6 +75,9 @@ const char kGuestInstanceID[] = "guest-instance-id";
 // Script that will be loaded by guest WebContents before other scripts.
 const char kPreloadScript[] = "preload";
 
+// Like --preload, but the passed argument is an URL.
+const char kPreloadUrl[] = "preload-url";
+
 // Whether the window should be transparent.
 const char kTransparent[] = "transparent";
 
diff --git a/atom/common/options_switches.h b/atom/common/options_switches.h
index 2dd48ee32a1..c9298618bdf 100644
--- a/atom/common/options_switches.h
+++ b/atom/common/options_switches.h
@@ -41,6 +41,7 @@ extern const char kPpapiFlashPath[];
 extern const char kPpapiFlashVersion[];
 extern const char kGuestInstanceID[];
 extern const char kPreloadScript[];
+extern const char kPreloadUrl[];
 extern const char kTransparent[];
 extern const char kType[];
 extern const char kDisableAutoHideCursor[];
diff --git a/docs/api/browser-window.md b/docs/api/browser-window.md
index e9d2c7f6feb..d74e999379b 100644
--- a/docs/api/browser-window.md
+++ b/docs/api/browser-window.md
@@ -48,8 +48,6 @@ Properties `width` and `height` are required.
 * `fullscreen` Boolean - Whether the window should show in fullscreen. When
   set to `false` the fullscreen button will also be hidden on OS X.
 * `skip-taskbar` Boolean - Whether to show the window in taskbar.
-* `zoom-factor` Number - The default zoom factor of the page, `3.0` represents
-`300%`.
 * `kiosk` Boolean - The kiosk mode.
 * `title` String - Default window title.
 * `icon` [NativeImage](native-image.md) - The window icon, when omitted on
@@ -57,8 +55,6 @@ Properties `width` and `height` are required.
 * `show` Boolean - Whether window should be shown when created.
 * `frame` Boolean - Specify `false` to create a
 [Frameless Window](frameless-window.md).
-* `node-integration` Boolean - Whether node integration is enabled. Default
-  is `true`.
 * `accept-first-mouse` Boolean - Whether the web view accepts a single
   mouse-down event that simultaneously activates the window.
 * `disable-auto-hide-cursor` Boolean - Whether to hide cursor when typing.
@@ -68,10 +64,6 @@ Properties `width` and `height` are required.
   than screen.
 * `dark-theme` Boolean - Forces using dark theme for the window, only works on
   some GTK+3 desktop environments.
-* `preload` String - Specifies a script that will be loaded before other
-  scripts run in the window. This script will always have access to node APIs
-  no matter whether node integration is turned on for the window, and the path
-  of `preload` script has to be absolute path.
 * `transparent` Boolean - Makes the window [transparent](frameless-window.md).
 * `type` String - Specifies the type of the window, possible types are
   `desktop`, `dock`, `toolbar`, `splash`, `notification`. This only works on
@@ -79,11 +71,25 @@ Properties `width` and `height` are required.
 * `standard-window` Boolean - Uses the OS X's standard window instead of the
   textured window. Defaults to `true`.
 * `web-preferences` Object - Settings of web page's features, properties:
+  * `node-integration` Boolean - Whether node integration is enabled. Default
+    is `true`.
+  * `preload` String - Specifies a script that will be loaded before other
+    scripts run in the page. This script will always have access to node APIs
+    no matter whether node integration is turned on for the page, and the path
+    of `preload` script has to be absolute path.
+  * `partition` String - Sets the session used by the page. If `partition`
+    starts with `persist:`, the page will use a persistent session available to
+    all pages in the app with the same `partition`. if there is no `persist:`
+    prefix, the page will use an in-memory session. By assigning the same
+    `partition`, multiple pages can share the same session. If the `partition`
+    is unset then default session of the app will be used.
+  * `zoom-factor` Number - The default zoom factor of the page, `3.0` represents
+    `300%`.
   * `javascript` Boolean
   * `web-security` Boolean - When setting `false`, it will disable the
-    same-origin policy (Usually using testing websites by people), and set `allow_displaying_insecure_content`
-    and `allow_running_insecure_content` to `true` if these two options are not
-    set by user.
+    same-origin policy (Usually using testing websites by people), and set
+    `allow_displaying_insecure_content` and `allow_running_insecure_content` to
+    `true` if these two options are not set by user.
   * `allow-displaying-insecure-content` Boolean - Allow an https page to display
     content like images from http URLs.
   * `allow-running-insecure-content` Boolean - Allow a https page to run
@@ -93,13 +99,7 @@ Properties `width` and `height` are required.
   * `text-areas-are-resizable` Boolean
   * `webgl` Boolean
   * `webaudio` Boolean
-  * `plugins` Boolean - Whether plugins should be enabled, currently only
-    `NPAPI` plugins are supported.
-  * `extra-plugin-dirs` Array - Array of paths that would be searched for
-    plugins. Note that if you want to add a directory under your app, you
-    should use `__dirname` or `process.resourcesPath` to join the paths to
-    make them absolute, using relative paths would make Electron search
-    under current working directory.
+  * `plugins` Boolean - Whether plugins should be enabled.
   * `experimental-features` Boolean
   * `experimental-canvas-features` Boolean
   * `subpixel-font-scaling` Boolean
diff --git a/docs/api/web-view-tag.md b/docs/api/web-view-tag.md
index c1b1f705e95..85039070216 100644
--- a/docs/api/web-view-tag.md
+++ b/docs/api/web-view-tag.md
@@ -138,16 +138,16 @@ If "on", the guest page will have web security disabled.
 <webview src="http://electron.atom.io" partition="electron"></webview>
 ```
 
-Sets the storage partition used by the `webview`. If the storage partition ID starts with `persist:`,
-the `webview` will use a persistent storage partition available to all `webview` in the app with
-the same storage partition ID. if there is no `persist:` prefix, the `webview` will
-use an in-memory storage partition. By assigning the same partition ID, multiple `webview`
-can share the same storage partition. If the storage partition ID is unset then default storage
-of the app will be used.
+Sets the session used by the page. If `partition` starts with `persist:`, the
+page will use a persistent session available to all pages in the app with the
+same `partition`. if there is no `persist:` prefix, the page will use an
+in-memory session. By assigning the same `partition`, multiple pages can share
+the same session. If the `partition` is unset then default session of the app
+will be used.
 
-This value can only be modified before the first navigation, since the storage partition of an active
-renderer process cannot change. Subsequent attempts to modify the value will fail with a
-DOM exception.
+This value can only be modified before the first navigation, since the session
+of an active renderer process cannot change. Subsequent attempts to modify the
+value will fail with a DOM exception.
 
 ## Methods
 
diff --git a/filenames.gypi b/filenames.gypi
index 2f97d01507e..b4d3bcb5e18 100644
--- a/filenames.gypi
+++ b/filenames.gypi
@@ -226,14 +226,16 @@
       'atom/browser/ui/x/window_state_watcher.h',
       'atom/browser/ui/x/x_window_utils.cc',
       'atom/browser/ui/x/x_window_utils.h',
+      'atom/browser/web_contents_preferences.cc',
+      'atom/browser/web_contents_preferences.h',
+      'atom/browser/web_dialog_helper.cc',
+      'atom/browser/web_dialog_helper.h',
       'atom/browser/web_view_constants.cc',
       'atom/browser/web_view_constants.h',
       'atom/browser/web_view_guest_delegate.cc',
       'atom/browser/web_view_guest_delegate.h',
       'atom/browser/web_view_manager.cc',
       'atom/browser/web_view_manager.h',
-      'atom/browser/web_dialog_helper.cc',
-      'atom/browser/web_dialog_helper.h',
       'atom/browser/window_list.cc',
       'atom/browser/window_list.h',
       'atom/browser/window_list_observer.h',
diff --git a/spec/webview-spec.coffee b/spec/webview-spec.coffee
index fe281510b40..3eeacb0ad0e 100644
--- a/spec/webview-spec.coffee
+++ b/spec/webview-spec.coffee
@@ -160,7 +160,7 @@ describe '<webview> tag', ->
         assert.equal e.message, 'undefined undefined undefined undefined'
         done()
       webview.src = "file://#{fixtures}/pages/c.html"
-      webview.partition = "test"
+      webview.partition = 'test1'
       document.body.appendChild webview
 
     it 'inserts node symbols when set', (done) ->
@@ -169,7 +169,7 @@ describe '<webview> tag', ->
         done()
       webview.setAttribute 'nodeintegration', 'on'
       webview.src = "file://#{fixtures}/pages/d.html"
-      webview.partition = "test"
+      webview.partition = 'test2'
       document.body.appendChild webview
 
     it 'isolates storage for different id', (done) ->
@@ -180,7 +180,7 @@ describe '<webview> tag', ->
       window.localStorage.setItem 'test', 'one'
       webview.addEventListener 'console-message', listener
       webview.src = "file://#{fixtures}/pages/partition/one.html"
-      webview.partition = "test"
+      webview.partition = 'test3'
       document.body.appendChild webview
 
     it 'uses current session storage when no id is provided', (done) ->
diff --git a/vendor/brightray b/vendor/brightray
index 4d8f5d879d4..8d64120b51b 160000
--- a/vendor/brightray
+++ b/vendor/brightray
@@ -1 +1 @@
-Subproject commit 4d8f5d879d484db54895c3456ded3a3d3246415d
+Subproject commit 8d64120b51b48be46eaa419957b965c0ccfc6c8f