Hoist begin frame sources out of scheduler

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 "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/completion_event.h"
@@ skipping 133 matching lines @@
   // thread.
   bool next_frame_is_newly_committed_frame_;
 
   bool inside_draw_;
   bool input_throttled_until_commit_;
 
   TaskRunnerProvider* task_runner_provider_;
 
   DelayedUniqueNotifier smoothness_priority_expiration_notifier_;
 
-  scoped_ptr<BeginFrameSource> external_begin_frame_source_;
+  scoped_ptr<BeginFrameSource> begin_frame_source_;
+  scoped_ptr<SyntheticBeginFrameSource> synthetic_frame_source_;

[Sami, 2016/03/08 19:15:25]

nit: synthetic_begin_frame_source_

 
   RenderingStatsInstrumentation* rendering_stats_instrumentation_;
 
   // Values used to keep track of frame durations. Used only in frame timing.
   BeginFrameArgs last_begin_main_frame_args_;
   BeginFrameArgs last_processed_begin_main_frame_args_;
 
   scoped_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_