gpu: Replace GpuMsg_GpuSwitched with mojom api.

content/gpu/gpu_child_thread.h

Index: content/gpu/gpu_child_thread.h
diff --git a/content/gpu/gpu_child_thread.h b/content/gpu/gpu_child_thread.h
index 4918d5cae6ef0c342c3c7ba40828b97cf5b46ec6..bba082542ccfe8dd482602c87c1e40276098410a 100644
--- a/content/gpu/gpu_child_thread.h
+++ b/content/gpu/gpu_child_thread.h
@@ -87,7 +87,6 @@ class GpuChildThread : public ChildThreadImpl,
 
   // ChildThreadImpl:.
   bool Send(IPC::Message* msg) override;
-  bool OnControlMessageReceived(const IPC::Message& msg) override;
 
   // IPC::Listener implementation via ChildThreadImpl:
   void OnAssociatedInterfaceRequest(
@@ -107,9 +106,6 @@ class GpuChildThread : public ChildThreadImpl,
   void OnFieldTrialGroupFinalized(const std::string& trial_name,
                                   const std::string& group_name) override;
 
-  // Message handlers.
-  void OnGpuSwitched();
-
   void BindServiceFactoryRequest(
       service_manager::mojom::ServiceFactoryRequest request);