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

cc/scheduler/begin_frame_source.h

 // Copyright 2014 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_BEGIN_FRAME_SOURCE_H_
 #define CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 99 matching lines @@
  public:
   BeginFrameSource();
   virtual ~BeginFrameSource();
 
   // Returns an identifier for this BeginFrameSource. Guaranteed unique within a
   // process, but not across processes. This is used to create BeginFrames that
   // originate at this source. Note that BeginFrameSources may pass on
   // BeginFrames created by other sources, with different IDs.
   uint32_t source_id() const { return source_id_; }
 
-  // BeginFrameObservers use DidFinishFrame to acknowledge that they have
-  // completed handling a BeginFrame.
-  //
-  // The DisplayScheduler uses these acknowledgments to trigger an early
-  // deadline once all BeginFrameObservers have completed a frame.
-  //
-  // They also provide back pressure to a frame source about frame processing
-  // (rather than toggling SetNeedsBeginFrames every frame). For example, the
-  // BackToBackFrameSource uses them to make sure only one frame is pending at a
-  // time.
-  //
-  // Note that the BeginFrameSource should not assume that the |ack| references
-  // a valid BeginFrame sent by the source. The |ack| may reference a BeginFrame
-  // sent by a different BeginFrameSource, and a malicious client may reference
-  // any invalid frame. The source is responsible for checking for
-  // validity/relevance of the BeginFrame itself.
-  // TODO(eseckler): Use BeginFrameAcks in DisplayScheduler as described above.
-  virtual void DidFinishFrame(BeginFrameObserver* obs,
-                              const BeginFrameAck& ack) = 0;
+  // BeginFrameObservers use DidFinishFrame to provide back pressure to a frame
+  // source about frame processing (rather than toggling SetNeedsBeginFrames
+  // every frame). For example, the BackToBackFrameSource uses them to make sure
+  // only one frame is pending at a time.
+  virtual void DidFinishFrame(BeginFrameObserver* obs) = 0;
 
   // Add/Remove an observer from the source. When no observers are added the BFS
   // should shut down its timers, disable vsync, etc.
   virtual void AddObserver(BeginFrameObserver* obs) = 0;
   virtual void RemoveObserver(BeginFrameObserver* obs) = 0;
 
   // Returns false if the begin frame source will just continue to produce
   // begin frames without waiting.
   virtual bool IsThrottled() const = 0;
 
   virtual void AsValueInto(base::trace_event::TracedValue* state) const;
 
  private:
   uint32_t source_id_;
 
   DISALLOW_COPY_AND_ASSIGN(BeginFrameSource);
 };
 
 // A BeginFrameSource that does nothing.
 class CC_EXPORT StubBeginFrameSource : public BeginFrameSource {
  public:
-  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;
 };
 
 // A frame source which ticks itself independently.
 class CC_EXPORT SyntheticBeginFrameSource : public BeginFrameSource {
  public:
   ~SyntheticBeginFrameSource() override;
 
   virtual void OnUpdateVSyncParameters(base::TimeTicks timebase,
                                        base::TimeDelta interval) = 0;
   // This overrides any past or future interval from updating vsync parameters.
   virtual void SetAuthoritativeVSyncInterval(base::TimeDelta interval) = 0;
 };
 
 // A frame source which calls BeginFrame (at the next possible time) as soon as
 // an observer acknowledges the prior BeginFrame.
 class CC_EXPORT BackToBackBeginFrameSource : public SyntheticBeginFrameSource,
                                              public DelayBasedTimeSourceClient {
  public:
   explicit BackToBackBeginFrameSource(
       std::unique_ptr<DelayBasedTimeSource> time_source);
   ~BackToBackBeginFrameSource() override;
 
   // BeginFrameSource implementation.
   void AddObserver(BeginFrameObserver* obs) override;
   void RemoveObserver(BeginFrameObserver* obs) override;
-  void DidFinishFrame(BeginFrameObserver* obs,
-                      const BeginFrameAck& ack) override;
+  void DidFinishFrame(BeginFrameObserver* obs) override;
   bool IsThrottled() const override;
 
   // SyntheticBeginFrameSource implementation.
   void OnUpdateVSyncParameters(base::TimeTicks timebase,
                                base::TimeDelta interval) override {}
   void SetAuthoritativeVSyncInterval(base::TimeDelta interval) override {}
 
   // DelayBasedTimeSourceClient implementation.
   void OnTimerTick() override;
 
@@ skipping 12 matching lines @@
 class CC_EXPORT DelayBasedBeginFrameSource : public SyntheticBeginFrameSource,
                                              public DelayBasedTimeSourceClient {
  public:
   explicit DelayBasedBeginFrameSource(
       std::unique_ptr<DelayBasedTimeSource> time_source);
   ~DelayBasedBeginFrameSource() override;
 
   // BeginFrameSource implementation.
   void AddObserver(BeginFrameObserver* obs) override;
   void RemoveObserver(BeginFrameObserver* obs) override;
-  void DidFinishFrame(BeginFrameObserver* obs,
-                      const BeginFrameAck& ack) override {}
+  void DidFinishFrame(BeginFrameObserver* obs) override {}
   bool IsThrottled() const override;
 
   // SyntheticBeginFrameSource implementation.
   void OnUpdateVSyncParameters(base::TimeTicks timebase,
                                base::TimeDelta interval) override;
   void SetAuthoritativeVSyncInterval(base::TimeDelta interval) override;
 
   // DelayBasedTimeSourceClient implementation.
   void OnTimerTick() override;
 
@@ skipping 23 matching lines @@
 // an observable BeginFrameSource.
 class CC_EXPORT ExternalBeginFrameSource : public BeginFrameSource {
  public:
   // Client lifetime must be preserved by owner past the lifetime of this class.
   explicit ExternalBeginFrameSource(ExternalBeginFrameSourceClient* client);
   ~ExternalBeginFrameSource() override;
 
   // BeginFrameSource implementation.
   void AddObserver(BeginFrameObserver* obs) override;
   void RemoveObserver(BeginFrameObserver* obs) override;
-  void DidFinishFrame(BeginFrameObserver* obs,
-                      const BeginFrameAck& ack) override;
+  void DidFinishFrame(BeginFrameObserver* obs) override {}
   bool IsThrottled() const override;
   void AsValueInto(base::trace_event::TracedValue* state) const override;
 
   void OnSetBeginFrameSourcePaused(bool paused);
   void OnBeginFrame(const BeginFrameArgs& args);
 
  protected:
   BeginFrameArgs last_begin_frame_args_;
   std::unordered_set<BeginFrameObserver*> observers_;
   ExternalBeginFrameSourceClient* client_;
   bool paused_ = false;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ExternalBeginFrameSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_