[cc] Remove BeginFrameAck from BFS::DidFinishFrame and update tests.

cc/surfaces/primary_begin_frame_source.h

 // Copyright 2017 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_SURFACES_PRIMARY_BEGIN_FRAME_SOURCE_H_
 #define CC_SURFACES_PRIMARY_BEGIN_FRAME_SOURCE_H_
 
 #include "cc/scheduler/begin_frame_source.h"
 
 namespace cc {
@@ skipping 10 matching lines @@
 
   void OnBeginFrameSourceAdded(BeginFrameSource* begin_frame_source);
   void OnBeginFrameSourceRemoved(BeginFrameSource* begin_frame_source);
 
   // BeginFrameObserver implementation.
   void OnBeginFrame(const BeginFrameArgs& args) override;
   const BeginFrameArgs& LastUsedBeginFrameArgs() const override;
   void OnBeginFrameSourcePausedChanged(bool paused) override;
 
   // BeginFrameSource implementation.
-  void DidFinishFrame(BeginFrameObserver* obs,
-                      const BeginFrameAck& ack) override;
+  void DidFinishFrame(BeginFrameObserver* obs) override;
   void AddObserver(BeginFrameObserver* obs) override;
   void RemoveObserver(BeginFrameObserver* obs) override;
   bool IsThrottled() const override;
 
   // ExternalBeginFrameSourceClient implementation.
   void OnNeedsBeginFrames(bool needs_begin_frames) override;
 
  private:
   ExternalBeginFrameSource begin_frame_source_;
   BeginFrameSource* current_begin_frame_source_ = nullptr;
 
   // The last begin frame args generated by the begin frame source.
   BeginFrameArgs last_begin_frame_args_;
 
   bool needs_begin_frames_ = false;
 
   base::flat_set<BeginFrameSource*> sources_;
 
   DISALLOW_COPY_AND_ASSIGN(PrimaryBeginFrameSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_PRIMARY_BEGIN_FRAME_SOURCE_H_