Make field trials activated in the GPU process be reflected in browser.

chrome/renderer/chrome_render_thread_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_THREAD_OBSERVER_H_
 #define CHROME_RENDERER_CHROME_RENDER_THREAD_OBSERVER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 12 matching lines @@
 }
 
 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 ChromeRenderThreadObserver : public content::RenderThreadObserver {
+class ChromeRenderThreadObserver : public content::RenderThreadObserver,
+                                   public base::FieldTrialList::Observer {

[Lei Zhang, 2016/06/06 23:18:20]

IWYU: #include "base/metrics/field_trial.h"

[Alexei Svitkine (slow), 2016/06/07 14:48:42]

Done.

  public:
   ChromeRenderThreadObserver();
   ~ChromeRenderThreadObserver() override;
 
   static bool is_incognito_process() { return is_incognito_process_; }
 
   // Returns a pointer to the content setting rules owned by
   // |ChromeRenderThreadObserver|.
   const RendererContentSettingRules* content_setting_rules() const;
 
  private:
   // Initializes field trial state change observation and notifies the browser
   // of any field trials that might have already been activated.
   void InitFieldTrialObserving(const base::CommandLine& command_line);
 
   // content::RenderThreadObserver:
   bool OnControlMessageReceived(const IPC::Message& message) override;
 
+  // base::FieldTrialList::Observer:
+  void OnFieldTrialGroupFinalized(const std::string& trial_name,
+                                  const std::string& group_name) 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& trial_name,
                             const std::string& group_name);
 
   static bool is_incognito_process_;
   std::unique_ptr<content::ResourceDispatcherDelegate> resource_delegate_;
   RendererContentSettingRules content_setting_rules_;
   chrome_variations::ChildProcessFieldTrialSyncer field_trial_syncer_;
 
   base::WeakPtrFactory<ChromeRenderThreadObserver> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeRenderThreadObserver);
 };
 
 #endif  // CHROME_RENDERER_CHROME_RENDER_THREAD_OBSERVER_H_