Reimplement vsync latency UMA to be based on BeginImplFrame rather than BeginMainFrame

cc/scheduler/compositor_timing_history.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_COMPOSITOR_TIMING_HISTORY_H_
 #define CC_SCHEDULER_COMPOSITOR_TIMING_HISTORY_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 36 matching lines @@
   virtual base::TimeDelta CommitToReadyToActivateDurationEstimate() const;
   virtual base::TimeDelta PrepareTilesDurationEstimate() const;
   virtual base::TimeDelta ActivateDurationEstimate() const;
   virtual base::TimeDelta DrawDurationEstimate() const;
 
   // State that affects when events should be expected/recorded/reported.
   void SetRecordingEnabled(bool enabled);
   void DidCreateAndInitializeCompositorFrameSink();
 
   // Events to be timed.
-  void WillBeginImplFrame(bool new_active_tree_is_likely);
+  void WillBeginImplFrame(bool new_active_tree_is_likely,
+                          base::TimeTicks frame_time,
+                          BeginFrameArgs::BeginFrameArgsType frame_type,
+                          base::TimeTicks now);
   void WillFinishImplFrame(bool needs_redraw);
   void BeginImplFrameNotExpectedSoon();
   void WillBeginMainFrame(bool on_critical_path,
-                          base::TimeTicks main_frame_time,
-                          BeginFrameArgs::BeginFrameArgsType frame_type);
+                          base::TimeTicks main_frame_time);
   void BeginMainFrameStarted(base::TimeTicks main_thread_start_time);
   void BeginMainFrameAborted();
   void DidCommit();
   void WillPrepareTiles();
   void DidPrepareTiles();
   void ReadyToActivate();
   void WillActivate();
   void DidActivate();
   void DrawAborted();
   void WillDraw();
@@ skipping 52 matching lines @@
   std::unique_ptr<UMAReporter> uma_reporter_;
   RenderingStatsInstrumentation* rendering_stats_instrumentation_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CompositorTimingHistory);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_COMPOSITOR_TIMING_HISTORY_H_