Send all field trials from the browser.

chrome/renderer/chrome_render_process_observer.h

 // 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_RENDERER_CHROME_RENDER_PROCESS_OBSERVER_H_
 #define CHROME_RENDERER_CHROME_RENDER_PROCESS_OBSERVER_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/metrics/field_trial.h"
 #include "components/content_settings/core/common/content_settings.h"
 #include "content/public/renderer/render_process_observer.h"
 
 class ChromeContentRendererClient;
 class GURL;
 struct ContentSettings;
 
 namespace content {
 class ResourceDispatcherDelegate;
 }
 
 // This class filters the incoming control messages (i.e. ones not destined for
 // a RenderView) for Chrome specific messages that the content layer doesn't
 // happen.  If a few messages are related, they should probably have their own
 // observer.
-class ChromeRenderProcessObserver : public content::RenderProcessObserver {
+class ChromeRenderProcessObserver : public content::RenderProcessObserver,
+                                    public base::FieldTrialList::Observer {
  public:
   explicit ChromeRenderProcessObserver(
       ChromeContentRendererClient* client);
   ~ChromeRenderProcessObserver() override;
 
   static bool is_incognito_process() { return is_incognito_process_; }
 
   // Returns a pointer to the content setting rules owned by
   // |ChromeRenderProcessObserver|.
   const RendererContentSettingRules* content_setting_rules() const;
 
  private:
   // RenderProcessObserver implementation.
   bool OnControlMessageReceived(const IPC::Message& message) override;
   void WebKitInitialized() override;
   void OnRenderProcessShutdown() override;
 
   void OnSetIsIncognitoProcess(bool is_incognito_process);
   void OnSetContentSettingsForCurrentURL(
       const GURL& url, const ContentSettings& content_settings);
   void OnSetContentSettingRules(const RendererContentSettingRules& rules);
   void OnGetCacheResourceStats();
   void OnSetFieldTrialGroup(const std::string& fiel_trial_name,
                             const std::string& group_name);
   void OnGetV8HeapStats();
+  void OnFieldTrialGroupFinalized(const std::string& trial_name,

[Alexei Svitkine (slow), 2014/11/07 15:51:02]

This is implementing base::FieldTrialList::Observer, so actually please put this
in a separate section with the following comment above it:

// base::FieldTrialList::Observer:

I suggest put the section above the OnSetIsIncognitoProcess and separating it by
newlines between above and below it.

[Georges Khalil, 2014/11/07 16:44:23]

Done.

+                                  const std::string& group_name) override;
 
   static bool is_incognito_process_;
   scoped_ptr<content::ResourceDispatcherDelegate> resource_delegate_;
   ChromeContentRendererClient* client_;
   // If true, the web cache shall be cleared before the next navigation event.
   bool clear_cache_pending_;
   RendererContentSettingRules content_setting_rules_;
 
   bool webkit_initialized_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeRenderProcessObserver);
 };
 
 #endif  // CHROME_RENDERER_CHROME_RENDER_PROCESS_OBSERVER_H_