REVIEW: register BrowserChildProcessObserver once main message loop is ready

atom/browser/api/atom_api_app.cc

@@ -532,7 +532,6 @@ App::App(v8::Isolate* isolate) {
   static_cast<AtomBrowserClient*>(AtomBrowserClient::Get())->set_delegate(this);
   Browser::Get()->AddObserver(this);
   content::GpuDataManager::GetInstance()->AddObserver(this);
-  content::BrowserChildProcessObserver::Add(this);
   base::ProcessId pid = base::GetCurrentProcId();
   std::unique_ptr<atom::ProcessMetric> process_metric(
       new atom::ProcessMetric(
@@ -597,6 +596,10 @@ void App::OnAccessibilitySupportChanged() {
   Emit("accessibility-support-changed", IsAccessibilitySupportEnabled());
 }
 
+void App::OnPreMainMessageLoopRun() {
+  content::BrowserChildProcessObserver::Add(this);
+}
+
 #if defined(OS_MACOSX)
 void App::OnWillContinueUserActivity(
     bool* prevent_default,

atom/browser/api/atom_api_app.h

@@ -104,6 +104,7 @@ class App : public AtomBrowserClient::Delegate,
   void OnLogin(LoginHandler* login_handler,
                const base::DictionaryValue& request_details) override;
   void OnAccessibilitySupportChanged() override;
+  void OnPreMainMessageLoopRun() override;
 #if defined(OS_MACOSX)
   void OnWillContinueUserActivity(
       bool* prevent_default,

atom/browser/atom_browser_main_parts.cc

@@ -128,6 +128,10 @@ void AtomBrowserMainParts::PostEarlyInitialization() {
   bridge_task_runner_ = new BridgeTaskRunner;
   base::ThreadTaskRunnerHandle handle(bridge_task_runner_);
 
+  base::FilePath user_dir;
+  PathService::Get(brightray::DIR_USER_DATA, &user_dir);
+  process_singleton_.reset(new ProcessSingleton(user_dir));
+
   // The ProxyResolverV8 has setup a complete V8 environment, in order to
   // avoid conflicts we only initialize our V8 environment after that.
   js_env_.reset(new JavascriptEnvironment);
@@ -184,6 +188,9 @@ void AtomBrowserMainParts::PreMainMessageLoopRun() {
   bridge_task_runner_->MessageLoopIsReady();
   bridge_task_runner_ = nullptr;
 
+  // Notify observers that main thread message loop was initialized.
+  Browser::Get()->PreMainMessageLoopRun();
+
 #if defined(USE_X11)
   libgtkui::GtkInitFromCommandLine(*base::CommandLine::ForCurrentProcess());
 #endif
@@ -211,10 +218,6 @@ void AtomBrowserMainParts::PostMainMessageLoopStart() {
 #endif
   device::GeolocationProvider::SetGeolocationDelegate(
       new AtomGeolocationDelegate());
-
-  base::FilePath user_dir;
-  PathService::Get(brightray::DIR_USER_DATA, &user_dir);
-  process_singleton_.reset(new ProcessSingleton(user_dir));
 }
 
 void AtomBrowserMainParts::PostMainMessageLoopRun() {

atom/browser/browser.cc

@@ -203,6 +203,12 @@ void Browser::RequestLogin(
     observer.OnLogin(login_handler, *(request_details.get()));
 }
 
+void Browser::PreMainMessageLoopRun() {
+  for (BrowserObserver& observer : observers_) {
+    observer.OnPreMainMessageLoopRun();
+  }
+}
+
 void Browser::NotifyAndShutdown() {
   if (is_shutdown_)
     return;

atom/browser/browser.h

@@ -224,6 +224,8 @@ class Browser : public WindowListObserver {
   void RequestLogin(LoginHandler* login_handler,
                     std::unique_ptr<base::DictionaryValue> request_details);
 
+  void PreMainMessageLoopRun();
+
   void AddObserver(BrowserObserver* obs) {
     observers_.AddObserver(obs);
   }

atom/browser/browser_observer.h

@@ -55,6 +55,9 @@ class BrowserObserver {
   // The browser's accessibility suppport has changed.
   virtual void OnAccessibilitySupportChanged() {}
 
+  // The app message loop is ready
+  virtual void OnPreMainMessageLoopRun() {}
+
 #if defined(OS_MACOSX)
   // The browser wants to report that an user activity will resume. (macOS only)
   virtual void OnWillContinueUserActivity(