[cc] Set BeginFrame sequence numbers on CompositorFrames from Scheduler.

cc/scheduler/scheduler.h

 // Copyright 2011 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_SCHEDULER_SCHEDULER_H_
 #define CC_SCHEDULER_SCHEDULER_H_
 
 #include <deque>
 #include <memory>
 #include <string>
@@ skipping 134 matching lines @@
   void SetDeferCommits(bool defer_commits);
 
   std::unique_ptr<base::trace_event::ConvertableToTraceFormat> AsValue() const;
 
   void SetVideoNeedsBeginFrames(bool video_needs_begin_frames);
 
   const BeginFrameSource* begin_frame_source() const {
     return begin_frame_source_;
   }
 
+  BeginFrameAck CurrentBeginFrameAckForActiveTree() const;
+
  protected:
   // Virtual for testing.
   virtual base::TimeTicks Now() const;
 
   const SchedulerSettings settings_;
   // Not owned.
   SchedulerClient* client_;
   int layer_tree_host_id_;
   base::SingleThreadTaskRunner* task_runner_;
 
@@ skipping 51 matching lines @@
   }
 
   base::WeakPtrFactory<Scheduler> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Scheduler);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_SCHEDULER_H_