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

chrome/common/variations/child_process_field_trial_syncer.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 CHROME_COMMON_VARIATIONS_CHILD_PROCESS_FIELD_TRIAL_SYNCER_H_
 #define CHROME_COMMON_VARIATIONS_CHILD_PROCESS_FIELD_TRIAL_SYNCER_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/metrics/field_trial.h"
-#include "ipc/ipc_sender.h"
 
 namespace base {
 class CommandLine;
 }
 
 namespace chrome_variations {
 
 // ChildProcessFieldTrialSyncer is a utility class that's responsible for
 // syncing the "activated" state of field trials between browser and child
 // processes. Specifically, when a field trial is activated in the browser, it
 // also activates it in the child process and when a field trial is activated
 // in the child process, it notifies the browser process to activate it.
-class ChildProcessFieldTrialSyncer : public base::FieldTrialList::Observer {
+class ChildProcessFieldTrialSyncer {
  public:
   // ChildProcessFieldTrialSyncer constructor taking an externally owned
-  // |ipc_sender| param for sending ChromeViewHostMsg_FieldTrialActivated IPCs
-  // to the browser process. The |ipc_sender| must outlive this object.
-  explicit ChildProcessFieldTrialSyncer(IPC::Sender* ipc_sender);
-  ~ChildProcessFieldTrialSyncer() override;
+  // |observer| param that's responsible for sending IPCs to the browser process
+  // when a trial is activated. The |observer| must outlive this object.
+  explicit ChildProcessFieldTrialSyncer(
+      base::FieldTrialList::Observer* observer);
+  ~ChildProcessFieldTrialSyncer();
 
   // 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);
 
   // Handler for messages from the browser process notifying the child process
   // that a field trial was activated.
   void OnSetFieldTrialGroup(const std::string& trial_name,
                             const std::string& group_name);
 
  private:
-  // base::FieldTrialList::Observer:
-  void OnFieldTrialGroupFinalized(const std::string& trial_name,
-                                  const std::string& group_name) override;
-
-  IPC::Sender* const ipc_sender_;
+  base::FieldTrialList::Observer* const observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildProcessFieldTrialSyncer);
 };
 
 }  // namespace chrome_variations
 
 #endif  // CHROME_COMMON_VARIATIONS_CHILD_PROCESS_FIELD_TRIAL_SYNCER_H_