Copy some relevant files over from Chromium

atom/browser/process_singleton.h

@@ -0,0 +1,183 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_PROCESS_SINGLETON_H_
+#define CHROME_BROWSER_PROCESS_SINGLETON_H_
+
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#endif  // defined(OS_WIN)
+
+#include <set>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/command_line.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "base/memory/ref_counted.h"
+#include "base/process/process.h"
+#include "base/threading/non_thread_safe.h"
+#include "ui/gfx/native_widget_types.h"
+
+#if defined(OS_POSIX) && !defined(OS_ANDROID)
+#include "base/files/scoped_temp_dir.h"
+#endif
+
+#if defined(OS_WIN)
+#include "base/win/message_window.h"
+#endif  // defined(OS_WIN)
+
+namespace base {
+class CommandLine;
+}
+
+// ProcessSingleton ----------------------------------------------------------
+//
+// This class allows different browser processes to communicate with
+// each other.  It is named according to the user data directory, so
+// we can be sure that no more than one copy of the application can be
+// running at once with a given data directory.
+//
+// Implementation notes:
+// - the Windows implementation uses an invisible global message window;
+// - the Linux implementation uses a Unix domain socket in the user data dir.
+
+class ProcessSingleton : public base::NonThreadSafe {
+ public:
+  enum NotifyResult {
+    PROCESS_NONE,
+    PROCESS_NOTIFIED,
+    PROFILE_IN_USE,
+    LOCK_ERROR,
+  };
+
+  // Implement this callback to handle notifications from other processes. The
+  // callback will receive the command line and directory with which the other
+  // Chrome process was launched. Return true if the command line will be
+  // handled within the current browser instance or false if the remote process
+  // should handle it (i.e., because the current process is shutting down).
+  using NotificationCallback =
+      base::Callback<bool(const base::CommandLine& command_line,
+                          const base::FilePath& current_directory)>;
+
+  ProcessSingleton(const base::FilePath& user_data_dir,
+                   const NotificationCallback& notification_callback);
+  ~ProcessSingleton();
+
+  // Notify another process, if available. Otherwise sets ourselves as the
+  // singleton instance. Returns PROCESS_NONE if we became the singleton
+  // instance. Callers are guaranteed to either have notified an existing
+  // process or have grabbed the singleton (unless the profile is locked by an
+  // unreachable process).
+  // TODO(brettw): Make the implementation of this method non-platform-specific
+  // by making Linux re-use the Windows implementation.
+  NotifyResult NotifyOtherProcessOrCreate();
+
+  // Sets ourself up as the singleton instance.  Returns true on success.  If
+  // false is returned, we are not the singleton instance and the caller must
+  // exit.
+  // NOTE: Most callers should generally prefer NotifyOtherProcessOrCreate() to
+  // this method, only callers for whom failure is preferred to notifying
+  // another process should call this directly.
+  bool Create();
+
+  // Clear any lock state during shutdown.
+  void Cleanup();
+
+#if defined(OS_POSIX) && !defined(OS_ANDROID)
+  static void DisablePromptForTesting();
+#endif
+#if defined(OS_WIN)
+  // Called to query whether to kill a hung browser process that has visible
+  // windows. Return true to allow killing the hung process.
+  using ShouldKillRemoteProcessCallback = base::Callback<bool()>;
+  void OverrideShouldKillRemoteProcessCallbackForTesting(
+      const ShouldKillRemoteProcessCallback& display_dialog_callback);
+#endif
+
+ protected:
+  // Notify another process, if available.
+  // Returns true if another process was found and notified, false if we should
+  // continue with the current process.
+  // On Windows, Create() has to be called before this.
+  NotifyResult NotifyOtherProcess();
+
+#if defined(OS_POSIX) && !defined(OS_ANDROID)
+  // Exposed for testing.  We use a timeout on Linux, and in tests we want
+  // this timeout to be short.
+  NotifyResult NotifyOtherProcessWithTimeout(
+      const base::CommandLine& command_line,
+      int retry_attempts,
+      const base::TimeDelta& timeout,
+      bool kill_unresponsive);
+  NotifyResult NotifyOtherProcessWithTimeoutOrCreate(
+      const base::CommandLine& command_line,
+      int retry_attempts,
+      const base::TimeDelta& timeout);
+  void OverrideCurrentPidForTesting(base::ProcessId pid);
+  void OverrideKillCallbackForTesting(
+      const base::Callback<void(int)>& callback);
+#endif
+
+ private:
+  NotificationCallback notification_callback_;  // Handler for notifications.
+
+#if defined(OS_WIN)
+  bool EscapeVirtualization(const base::FilePath& user_data_dir);
+
+  HWND remote_window_;  // The HWND_MESSAGE of another browser.
+  base::win::MessageWindow window_;  // The message-only window.
+  bool is_virtualized_;  // Stuck inside Microsoft Softricity VM environment.
+  HANDLE lock_file_;
+  base::FilePath user_data_dir_;
+  ShouldKillRemoteProcessCallback should_kill_remote_process_callback_;
+#elif defined(OS_POSIX) && !defined(OS_ANDROID)
+  // Return true if the given pid is one of our child processes.
+  // Assumes that the current pid is the root of all pids of the current
+  // instance.
+  bool IsSameChromeInstance(pid_t pid);
+
+  // Extract the process's pid from a symbol link path and if it is on
+  // the same host, kill the process, unlink the lock file and return true.
+  // If the process is part of the same chrome instance, unlink the lock file
+  // and return true without killing it.
+  // If the process is on a different host, return false.
+  bool KillProcessByLockPath();
+
+  // Default function to kill a process, overridable by tests.
+  void KillProcess(int pid);
+
+  // Allow overriding for tests.
+  base::ProcessId current_pid_;
+
+  // Function to call when the other process is hung and needs to be killed.
+  // Allows overriding for tests.
+  base::Callback<void(int)> kill_callback_;
+
+  // Path in file system to the socket.
+  base::FilePath socket_path_;
+
+  // Path in file system to the lock.
+  base::FilePath lock_path_;
+
+  // Path in file system to the cookie file.
+  base::FilePath cookie_path_;
+
+  // Temporary directory to hold the socket.
+  base::ScopedTempDir socket_dir_;
+
+  // Helper class for linux specific messages.  LinuxWatcher is ref counted
+  // because it posts messages between threads.
+  class LinuxWatcher;
+  scoped_refptr<LinuxWatcher> watcher_;
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(ProcessSingleton);
+};
+
+#endif  // CHROME_BROWSER_PROCESS_SINGLETON_H_

atom/browser/process_singleton_startup_lock.cc

@@ -0,0 +1,53 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/process_singleton_startup_lock.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+
+ProcessSingletonStartupLock::ProcessSingletonStartupLock(
+    const ProcessSingleton::NotificationCallback& original_callback)
+    : locked_(true),
+      original_callback_(original_callback) {}
+
+ProcessSingletonStartupLock::~ProcessSingletonStartupLock() {}
+
+ProcessSingleton::NotificationCallback
+ProcessSingletonStartupLock::AsNotificationCallback() {
+  return base::Bind(&ProcessSingletonStartupLock::NotificationCallbackImpl,
+                    base::Unretained(this));
+}
+
+void ProcessSingletonStartupLock::Unlock() {
+  DCHECK(CalledOnValidThread());
+  locked_ = false;
+
+  // Replay the command lines of the messages which were received while the
+  // ProcessSingleton was locked. Only replay each message once.
+  std::set<DelayedStartupMessage> replayed_messages;
+  for (std::vector<DelayedStartupMessage>::const_iterator it =
+           saved_startup_messages_.begin();
+       it != saved_startup_messages_.end(); ++it) {
+    if (replayed_messages.find(*it) != replayed_messages.end())
+      continue;
+    original_callback_.Run(base::CommandLine(it->first), it->second);
+    replayed_messages.insert(*it);
+  }
+  saved_startup_messages_.clear();
+}
+
+bool ProcessSingletonStartupLock::NotificationCallbackImpl(
+    const base::CommandLine& command_line,
+    const base::FilePath& current_directory) {
+  if (locked_) {
+    // If locked, it means we are not ready to process this message because
+    // we are probably in a first run critical phase.
+    saved_startup_messages_.push_back(
+        std::make_pair(command_line.argv(), current_directory));
+    return true;
+  } else {
+    return original_callback_.Run(command_line, current_directory);
+  }
+}

atom/browser/process_singleton_startup_lock.h

@@ -0,0 +1,57 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_PROCESS_SINGLETON_STARTUP_LOCK_H_
+#define CHROME_BROWSER_PROCESS_SINGLETON_STARTUP_LOCK_H_
+
+#include <set>
+#include <utility>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/command_line.h"
+#include "base/files/file_path.h"
+#include "base/threading/non_thread_safe.h"
+#include "chrome/browser/process_singleton.h"
+
+// Provides a ProcessSingleton::NotificationCallback that can queue up
+// command-line invocations during startup and execute them when startup
+// completes.
+//
+// The object starts in a locked state. |Unlock()| must be called
+// when the process is prepared to handle command-line invocations.
+//
+// Once unlocked, notifications are forwarded to a wrapped NotificationCallback.
+class ProcessSingletonStartupLock : public base::NonThreadSafe {
+ public:
+  explicit ProcessSingletonStartupLock(
+      const ProcessSingleton::NotificationCallback& original_callback);
+  ~ProcessSingletonStartupLock();
+
+  // Returns the ProcessSingleton::NotificationCallback.
+  // The callback is only valid during the lifetime of the
+  // ProcessSingletonStartupLock instance.
+  ProcessSingleton::NotificationCallback AsNotificationCallback();
+
+  // Executes previously queued command-line invocations and allows future
+  // invocations to be executed immediately.
+  void Unlock();
+
+  bool locked() { return locked_; }
+
+ private:
+  typedef std::pair<base::CommandLine::StringVector, base::FilePath>
+      DelayedStartupMessage;
+
+  bool NotificationCallbackImpl(const base::CommandLine& command_line,
+                                const base::FilePath& current_directory);
+
+  bool locked_;
+  std::vector<DelayedStartupMessage> saved_startup_messages_;
+  ProcessSingleton::NotificationCallback original_callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProcessSingletonStartupLock);
+};
+
+#endif  // CHROME_BROWSER_PROCESS_SINGLETON_STARTUP_LOCK_H_

atom/browser/process_singleton_win.cc

@@ -0,0 +1,441 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/process_singleton.h"
+
+#include <shellapi.h>
+
+#include "base/base_paths.h"
+#include "base/bind.h"
+#include "base/command_line.h"
+#include "base/files/file_path.h"
+#include "base/process/process.h"
+#include "base/process/process_info.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/time/time.h"
+#include "base/win/metro.h"
+#include "base/win/registry.h"
+#include "base/win/scoped_handle.h"
+#include "base/win/windows_version.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/browser_process_platform_part.h"
+#include "chrome/browser/chrome_process_finder_win.h"
+#include "chrome/browser/metro_utils/metro_chrome_win.h"
+#include "chrome/browser/shell_integration.h"
+#include "chrome/browser/ui/simple_message_box.h"
+#include "chrome/common/chrome_constants.h"
+#include "chrome/common/chrome_paths.h"
+#include "chrome/common/chrome_paths_internal.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/grit/chromium_strings.h"
+#include "chrome/installer/util/wmi.h"
+#include "content/public/common/result_codes.h"
+#include "net/base/escape.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/gfx/win/hwnd_util.h"
+
+namespace {
+
+const char kLockfile[] = "lockfile";
+
+const int kMetroChromeActivationTimeoutMs = 3000;
+
+// A helper class that acquires the given |mutex| while the AutoLockMutex is in
+// scope.
+class AutoLockMutex {
+ public:
+  explicit AutoLockMutex(HANDLE mutex) : mutex_(mutex) {
+    DWORD result = ::WaitForSingleObject(mutex_, INFINITE);
+    DPCHECK(result == WAIT_OBJECT_0) << "Result = " << result;
+  }
+
+  ~AutoLockMutex() {
+    BOOL released = ::ReleaseMutex(mutex_);
+    DPCHECK(released);
+  }
+
+ private:
+  HANDLE mutex_;
+  DISALLOW_COPY_AND_ASSIGN(AutoLockMutex);
+};
+
+// A helper class that releases the given |mutex| while the AutoUnlockMutex is
+// in scope and immediately re-acquires it when going out of scope.
+class AutoUnlockMutex {
+ public:
+  explicit AutoUnlockMutex(HANDLE mutex) : mutex_(mutex) {
+    BOOL released = ::ReleaseMutex(mutex_);
+    DPCHECK(released);
+  }
+
+  ~AutoUnlockMutex() {
+    DWORD result = ::WaitForSingleObject(mutex_, INFINITE);
+    DPCHECK(result == WAIT_OBJECT_0) << "Result = " << result;
+  }
+
+ private:
+  HANDLE mutex_;
+  DISALLOW_COPY_AND_ASSIGN(AutoUnlockMutex);
+};
+
+// Checks the visibility of the enumerated window and signals once a visible
+// window has been found.
+BOOL CALLBACK BrowserWindowEnumeration(HWND window, LPARAM param) {
+  bool* result = reinterpret_cast<bool*>(param);
+  *result = ::IsWindowVisible(window) != 0;
+  // Stops enumeration if a visible window has been found.
+  return !*result;
+}
+
+bool ParseCommandLine(const COPYDATASTRUCT* cds,
+                      base::CommandLine* parsed_command_line,
+                      base::FilePath* current_directory) {
+  // We should have enough room for the shortest command (min_message_size)
+  // and also be a multiple of wchar_t bytes. The shortest command
+  // possible is L"START\0\0" (empty current directory and command line).
+  static const int min_message_size = 7;
+  if (cds->cbData < min_message_size * sizeof(wchar_t) ||
+      cds->cbData % sizeof(wchar_t) != 0) {
+    LOG(WARNING) << "Invalid WM_COPYDATA, length = " << cds->cbData;
+    return false;
+  }
+
+  // We split the string into 4 parts on NULLs.
+  DCHECK(cds->lpData);
+  const std::wstring msg(static_cast<wchar_t*>(cds->lpData),
+                         cds->cbData / sizeof(wchar_t));
+  const std::wstring::size_type first_null = msg.find_first_of(L'\0');
+  if (first_null == 0 || first_null == std::wstring::npos) {
+    // no NULL byte, don't know what to do
+    LOG(WARNING) << "Invalid WM_COPYDATA, length = " << msg.length() <<
+      ", first null = " << first_null;
+    return false;
+  }
+
+  // Decode the command, which is everything until the first NULL.
+  if (msg.substr(0, first_null) == L"START") {
+    // Another instance is starting parse the command line & do what it would
+    // have done.
+    VLOG(1) << "Handling STARTUP request from another process";
+    const std::wstring::size_type second_null =
+        msg.find_first_of(L'\0', first_null + 1);
+    if (second_null == std::wstring::npos ||
+        first_null == msg.length() - 1 || second_null == msg.length()) {
+      LOG(WARNING) << "Invalid format for start command, we need a string in 4 "
+        "parts separated by NULLs";
+      return false;
+    }
+
+    // Get current directory.
+    *current_directory = base::FilePath(msg.substr(first_null + 1,
+                                                   second_null - first_null));
+
+    const std::wstring::size_type third_null =
+        msg.find_first_of(L'\0', second_null + 1);
+    if (third_null == std::wstring::npos ||
+        third_null == msg.length()) {
+      LOG(WARNING) << "Invalid format for start command, we need a string in 4 "
+        "parts separated by NULLs";
+    }
+
+    // Get command line.
+    const std::wstring cmd_line =
+        msg.substr(second_null + 1, third_null - second_null);
+    *parsed_command_line = base::CommandLine::FromString(cmd_line);
+    return true;
+  }
+  return false;
+}
+
+bool ProcessLaunchNotification(
+    const ProcessSingleton::NotificationCallback& notification_callback,
+    UINT message,
+    WPARAM wparam,
+    LPARAM lparam,
+    LRESULT* result) {
+  if (message != WM_COPYDATA)
+    return false;
+
+  // Handle the WM_COPYDATA message from another process.
+  const COPYDATASTRUCT* cds = reinterpret_cast<COPYDATASTRUCT*>(lparam);
+
+  base::CommandLine parsed_command_line(base::CommandLine::NO_PROGRAM);
+  base::FilePath current_directory;
+  if (!ParseCommandLine(cds, &parsed_command_line, &current_directory)) {
+    *result = TRUE;
+    return true;
+  }
+
+  *result = notification_callback.Run(parsed_command_line, current_directory) ?
+      TRUE : FALSE;
+  return true;
+}
+
+// Returns true if Chrome needs to be relaunched into Windows 8 immersive mode.
+// Following conditions apply:-
+// 1. Windows 8 or greater.
+// 2. Not in Windows 8 immersive mode.
+// 3. Chrome is default browser.
+// 4. Process integrity level is not high.
+// 5. The profile data directory is the default directory.
+// 6. Last used mode was immersive/machine is a tablet.
+// TODO(ananta)
+// Move this function to a common place as the Windows 8 delegate_execute
+// handler can possibly use this.
+bool ShouldLaunchInWindows8ImmersiveMode(const base::FilePath& user_data_dir) {
+  // Returning false from this function doesn't mean we don't launch immersive
+  // mode in Aura. This function is specifically called in case when we need
+  // to relaunch desktop launched chrome into immersive mode through 'relaunch'
+  // menu. In case of Aura, we will use delegate_execute to do the relaunch.
+  return false;
+}
+
+bool DisplayShouldKillMessageBox() {
+  return chrome::ShowMessageBox(
+             NULL, l10n_util::GetStringUTF16(IDS_PRODUCT_NAME),
+             l10n_util::GetStringUTF16(IDS_BROWSER_HUNGBROWSER_MESSAGE),
+             chrome::MESSAGE_BOX_TYPE_QUESTION) !=
+         chrome::MESSAGE_BOX_RESULT_NO;
+}
+
+}  // namespace
+
+// Microsoft's Softricity virtualization breaks the sandbox processes.
+// So, if we detect the Softricity DLL we use WMI Win32_Process.Create to
+// break out of the virtualization environment.
+// http://code.google.com/p/chromium/issues/detail?id=43650
+bool ProcessSingleton::EscapeVirtualization(
+    const base::FilePath& user_data_dir) {
+  if (::GetModuleHandle(L"sftldr_wow64.dll") ||
+      ::GetModuleHandle(L"sftldr.dll")) {
+    int process_id;
+    if (!installer::WMIProcess::Launch(::GetCommandLineW(), &process_id))
+      return false;
+    is_virtualized_ = true;
+    // The new window was spawned from WMI, and won't be in the foreground.
+    // So, first we sleep while the new chrome.exe instance starts (because
+    // WaitForInputIdle doesn't work here). Then we poll for up to two more
+    // seconds and make the window foreground if we find it (or we give up).
+    HWND hwnd = 0;
+    ::Sleep(90);
+    for (int tries = 200; tries; --tries) {
+      hwnd = chrome::FindRunningChromeWindow(user_data_dir);
+      if (hwnd) {
+        ::SetForegroundWindow(hwnd);
+        break;
+      }
+      ::Sleep(10);
+    }
+    return true;
+  }
+  return false;
+}
+
+ProcessSingleton::ProcessSingleton(
+    const base::FilePath& user_data_dir,
+    const NotificationCallback& notification_callback)
+    : notification_callback_(notification_callback),
+      is_virtualized_(false),
+      lock_file_(INVALID_HANDLE_VALUE),
+      user_data_dir_(user_data_dir),
+      should_kill_remote_process_callback_(
+          base::Bind(&DisplayShouldKillMessageBox)) {
+}
+
+ProcessSingleton::~ProcessSingleton() {
+  if (lock_file_ != INVALID_HANDLE_VALUE)
+    ::CloseHandle(lock_file_);
+}
+
+// Code roughly based on Mozilla.
+ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcess() {
+  if (is_virtualized_)
+    return PROCESS_NOTIFIED;  // We already spawned the process in this case.
+  if (lock_file_ == INVALID_HANDLE_VALUE && !remote_window_) {
+    return LOCK_ERROR;
+  } else if (!remote_window_) {
+    return PROCESS_NONE;
+  }
+
+  switch (chrome::AttemptToNotifyRunningChrome(remote_window_, false)) {
+    case chrome::NOTIFY_SUCCESS:
+      return PROCESS_NOTIFIED;
+    case chrome::NOTIFY_FAILED:
+      remote_window_ = NULL;
+      return PROCESS_NONE;
+    case chrome::NOTIFY_WINDOW_HUNG:
+      // Fall through and potentially terminate the hung browser.
+      break;
+  }
+
+  DWORD process_id = 0;
+  DWORD thread_id = ::GetWindowThreadProcessId(remote_window_, &process_id);
+  if (!thread_id || !process_id) {
+    remote_window_ = NULL;
+    return PROCESS_NONE;
+  }
+  base::Process process = base::Process::Open(process_id);
+
+  // The window is hung. Scan for every window to find a visible one.
+  bool visible_window = false;
+  ::EnumThreadWindows(thread_id,
+                      &BrowserWindowEnumeration,
+                      reinterpret_cast<LPARAM>(&visible_window));
+
+  // If there is a visible browser window, ask the user before killing it.
+  if (visible_window && !should_kill_remote_process_callback_.Run()) {
+    // The user denied. Quit silently.
+    return PROCESS_NOTIFIED;
+  }
+
+  // Time to take action. Kill the browser process.
+  process.Terminate(content::RESULT_CODE_HUNG, true);
+  remote_window_ = NULL;
+  return PROCESS_NONE;
+}
+
+ProcessSingleton::NotifyResult
+ProcessSingleton::NotifyOtherProcessOrCreate() {
+  ProcessSingleton::NotifyResult result = PROCESS_NONE;
+  if (!Create()) {
+    result = NotifyOtherProcess();
+    if (result == PROCESS_NONE)
+      result = PROFILE_IN_USE;
+  } else {
+    g_browser_process->platform_part()->PlatformSpecificCommandLineProcessing(
+        *base::CommandLine::ForCurrentProcess());
+  }
+  return result;
+}
+
+// Look for a Chrome instance that uses the same profile directory. If there
+// isn't one, create a message window with its title set to the profile
+// directory path.
+bool ProcessSingleton::Create() {
+  static const wchar_t kMutexName[] = L"Local\\ChromeProcessSingletonStartup!";
+  static const wchar_t kMetroActivationEventName[] =
+      L"Local\\ChromeProcessSingletonStartupMetroActivation!";
+
+  remote_window_ = chrome::FindRunningChromeWindow(user_data_dir_);
+  if (!remote_window_ && !EscapeVirtualization(user_data_dir_)) {
+    // Make sure we will be the one and only process creating the window.
+    // We use a named Mutex since we are protecting against multi-process
+    // access. As documented, it's clearer to NOT request ownership on creation
+    // since it isn't guaranteed we will get it. It is better to create it
+    // without ownership and explicitly get the ownership afterward.
+    base::win::ScopedHandle only_me(::CreateMutex(NULL, FALSE, kMutexName));
+    if (!only_me.IsValid()) {
+      DPLOG(FATAL) << "CreateMutex failed";
+      return false;
+    }
+
+    AutoLockMutex auto_lock_only_me(only_me.Get());
+
+    // We now own the mutex so we are the only process that can create the
+    // window at this time, but we must still check if someone created it
+    // between the time where we looked for it above and the time the mutex
+    // was given to us.
+    remote_window_ = chrome::FindRunningChromeWindow(user_data_dir_);
+
+
+    // In Win8+, a new Chrome process launched in Desktop mode may need to be
+    // transmuted into Metro Chrome (see ShouldLaunchInWindows8ImmersiveMode for
+    // heuristics). To accomplish this, the current Chrome activates Metro
+    // Chrome, releases the startup mutex, and waits for metro Chrome to take
+    // the singleton. From that point onward, the command line for this Chrome
+    // process will be sent to Metro Chrome by the usual channels.
+    if (!remote_window_ && base::win::GetVersion() >= base::win::VERSION_WIN8 &&
+        !base::win::IsMetroProcess()) {
+      // |metro_activation_event| is created right before activating a Metro
+      // Chrome (note that there can only be one Metro Chrome process; by OS
+      // design); all following Desktop processes will then wait for this event
+      // to be signaled by Metro Chrome which will do so as soon as it grabs
+      // this singleton (should any of the waiting processes timeout waiting for
+      // the signal they will try to grab the singleton for themselves which
+      // will result in a forced Desktop Chrome launch in the worst case).
+      base::win::ScopedHandle metro_activation_event(
+          ::OpenEvent(SYNCHRONIZE, FALSE, kMetroActivationEventName));
+      if (!metro_activation_event.IsValid() &&
+          ShouldLaunchInWindows8ImmersiveMode(user_data_dir_)) {
+        // No Metro activation is under way, but the desire is to launch in
+        // Metro mode: activate and rendez-vous with the activated process.
+        metro_activation_event.Set(
+            ::CreateEvent(NULL, TRUE, FALSE, kMetroActivationEventName));
+        if (!chrome::ActivateMetroChrome()) {
+          // Failed to launch immersive Chrome, default to launching on Desktop.
+          LOG(ERROR) << "Failed to launch immersive chrome";
+          metro_activation_event.Close();
+        }
+      }
+
+      if (metro_activation_event.IsValid()) {
+        // Release |only_me| (to let Metro Chrome grab this singleton) and wait
+        // until the event is signaled (i.e. Metro Chrome was successfully
+        // activated). Ignore timeout waiting for |metro_activation_event|.
+        {
+          AutoUnlockMutex auto_unlock_only_me(only_me.Get());
+
+          DWORD result = ::WaitForSingleObject(metro_activation_event.Get(),
+                                               kMetroChromeActivationTimeoutMs);
+          DPCHECK(result == WAIT_OBJECT_0 || result == WAIT_TIMEOUT)
+              << "Result = " << result;
+        }
+
+        // Check if this singleton was successfully grabbed by another process
+        // (hopefully Metro Chrome). Failing to do so, this process will grab
+        // the singleton and launch in Desktop mode.
+        remote_window_ = chrome::FindRunningChromeWindow(user_data_dir_);
+      }
+    }
+
+    if (!remote_window_) {
+      // We have to make sure there is no Chrome instance running on another
+      // machine that uses the same profile.
+      base::FilePath lock_file_path = user_data_dir_.AppendASCII(kLockfile);
+      lock_file_ = ::CreateFile(lock_file_path.value().c_str(),
+                                GENERIC_WRITE,
+                                FILE_SHARE_READ,
+                                NULL,
+                                CREATE_ALWAYS,
+                                FILE_ATTRIBUTE_NORMAL |
+                                FILE_FLAG_DELETE_ON_CLOSE,
+                                NULL);
+      DWORD error = ::GetLastError();
+      LOG_IF(WARNING, lock_file_ != INVALID_HANDLE_VALUE &&
+          error == ERROR_ALREADY_EXISTS) << "Lock file exists but is writable.";
+      LOG_IF(ERROR, lock_file_ == INVALID_HANDLE_VALUE)
+          << "Lock file can not be created! Error code: " << error;
+
+      if (lock_file_ != INVALID_HANDLE_VALUE) {
+        // Set the window's title to the path of our user data directory so
+        // other Chrome instances can decide if they should forward to us.
+        bool result = window_.CreateNamed(
+            base::Bind(&ProcessLaunchNotification, notification_callback_),
+            user_data_dir_.value());
+        CHECK(result && window_.hwnd());
+      }
+
+      if (base::win::GetVersion() >= base::win::VERSION_WIN8) {
+        // Make sure no one is still waiting on Metro activation whether it
+        // succeeded (i.e., this is the Metro process) or failed.
+        base::win::ScopedHandle metro_activation_event(
+            ::OpenEvent(EVENT_MODIFY_STATE, FALSE, kMetroActivationEventName));
+        if (metro_activation_event.IsValid())
+          ::SetEvent(metro_activation_event.Get());
+      }
+    }
+  }
+
+  return window_.hwnd() != NULL;
+}
+
+void ProcessSingleton::Cleanup() {
+}
+
+void ProcessSingleton::OverrideShouldKillRemoteProcessCallbackForTesting(
+    const ShouldKillRemoteProcessCallback& display_dialog_callback) {
+  should_kill_remote_process_callback_ = display_dialog_callback;
+}