Revert of Remove default begin frame sources from the renderer

cc/trees/proxy_impl.h

 // Copyright 2015 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 CC_TREES_PROXY_IMPL_H_
 #define CC_TREES_PROXY_IMPL_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 48 matching lines @@
   // The members of this struct should be accessed on the impl thread only when
   // the main thread is blocked for a commit.
   struct BlockedMainCommitOnly {
     BlockedMainCommitOnly();
     ~BlockedMainCommitOnly();
     LayerTreeHost* layer_tree_host;
   };
 
   // LayerTreeHostImplClient implementation
   void DidLoseOutputSurfaceOnImplThread() override;
+  void CommitVSyncParameters(base::TimeTicks timebase,
+                             base::TimeDelta interval) override;
   void SetBeginFrameSource(BeginFrameSource* source) override;
   void SetEstimatedParentDrawTime(base::TimeDelta draw_time) override;
   void DidSwapBuffersCompleteOnImplThread() override;
   void OnCanDrawStateChanged(bool can_draw) override;
   void NotifyReadyToActivate() override;
   void NotifyReadyToDraw() override;
   // Please call these 3 functions through
   // LayerTreeHostImpl's SetNeedsRedraw(), SetNeedsRedrawRect() and
   // SetNeedsOneBeginImplFrame().
   void SetNeedsRedrawOnImplThread() override;
@@ skipping 50 matching lines @@
   bool next_frame_is_newly_committed_frame_;
 
   bool inside_draw_;
   bool input_throttled_until_commit_;
 
   TaskRunnerProvider* task_runner_provider_;
 
   DelayedUniqueNotifier smoothness_priority_expiration_notifier_;
 
   std::unique_ptr<BeginFrameSource> external_begin_frame_source_;
+  std::unique_ptr<BeginFrameSource> unthrottled_begin_frame_source_;
+  std::unique_ptr<SyntheticBeginFrameSource> synthetic_begin_frame_source_;
 
   RenderingStatsInstrumentation* rendering_stats_instrumentation_;
 
   std::unique_ptr<LayerTreeHostImpl> layer_tree_host_impl_;
 
   ChannelImpl* channel_impl_;
 
   // Use accessors instead of this variable directly.
   BlockedMainCommitOnly main_thread_blocked_commit_vars_unsafe_;
   BlockedMainCommitOnly& blocked_main_commit();
 
   DISALLOW_COPY_AND_ASSIGN(ProxyImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_PROXY_IMPL_H_