Convert ChromeViewMsg_SetFieldTrialGroup to use mojo.

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 35 matching lines @@
   visitedlink::VisitedLinkSlave* visited_link_slave() {
     return visited_link_slave_.get();
   }
 
  private:
   // content::RenderThreadObserver:
   void RegisterMojoInterfaces(
       content::AssociatedInterfaceRegistry* associated_interfaces) override;
   void UnregisterMojoInterfaces(
       content::AssociatedInterfaceRegistry* associated_interfaces) override;
-  bool OnControlMessageReceived(const IPC::Message& message) override;
   void OnRenderProcessShutdown() override;
 
   // base::FieldTrialList::Observer:
   void OnFieldTrialGroupFinalized(const std::string& trial_name,
                                   const std::string& group_name) override;
 
   // chrome::mojom::RendererConfiguration:
   void SetInitialConfiguration(bool is_incognito_process) override;
   void SetContentSettingRules(
       const RendererContentSettingRules& rules) override;
+  void SetFieldTrialGroup(const std::string& trial_name,
+                          const std::string& group_name) override;
 
   void OnRendererConfigurationAssociatedRequest(
       chrome::mojom::RendererConfigurationAssociatedRequest request);
 
-  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_;
   variations::ChildProcessFieldTrialSyncer field_trial_syncer_;
 
   std::unique_ptr<visitedlink::VisitedLinkSlave> visited_link_slave_;
 
   mojo::AssociatedBindingSet<chrome::mojom::RendererConfiguration>
       renderer_configuration_bindings_;
 
   base::WeakPtrFactory<ChromeRenderThreadObserver> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeRenderThreadObserver);
 };
 
 #endif  // CHROME_RENDERER_CHROME_RENDER_THREAD_OBSERVER_H_