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

content/public/gpu/content_gpu_client.h

 // Copyright 2016 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 CONTENT_PUBLIC_GPU_CONTENT_GPU_CLIENT_H_
 #define CONTENT_PUBLIC_GPU_CONTENT_GPU_CLIENT_H_
 
+#include "base/metrics/field_trial.h"
 #include "content/public/common/content_client.h"
 
 namespace gpu {
 class SyncPointManager;
 }
 
 namespace content {
 
 class ServiceRegistry;
 
 // Embedder API for participating in gpu logic.
 class CONTENT_EXPORT ContentGpuClient {
  public:
   virtual ~ContentGpuClient() {}
 
+  // Initializes the client. This sets up the field trial synchronization
+  // mechanism, which will notify |observer| when a field trial is activated,
+  // which should be used to inform the browser process of this state.
+  virtual void Initialize(base::FieldTrialList::Observer* observer) {}
+
   // Allows client to register Mojo services in |registry| on the GPU process.
   // The registered services will be exposed to the browser process through
   // GpuProcessHost.
   virtual void RegisterMojoServices(ServiceRegistry* registry) {}
 
   // Allows client to supply a SyncPointManager instance instead of having
   // content internally create one.
   virtual gpu::SyncPointManager* GetSyncPointManager();
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_GPU_CONTENT_GPU_CLIENT_H_