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

cc/scheduler/compositor_timing_history.cc

Index: cc/scheduler/compositor_timing_history.cc
diff --git a/cc/scheduler/compositor_timing_history.cc b/cc/scheduler/compositor_timing_history.cc
index 0e88a8af073c93f361fa0adcf08266e661f4a9c1..dda74e75da773d41653dc63cdd126df322e5ed76 100644
--- a/cc/scheduler/compositor_timing_history.cc
+++ b/cc/scheduler/compositor_timing_history.cc
@@ -26,7 +26,7 @@ class CompositorTimingHistory::UMAReporter {
   virtual void AddDrawInterval(base::TimeDelta interval) = 0;
 
   // Latency measurements
-  virtual void AddBeginMainFrameLatency(base::TimeDelta delta) = 0;
+  virtual void AddBeginImplFrameLatency(base::TimeDelta delta) = 0;
   virtual void AddBeginMainFrameQueueDurationCriticalDuration(
       base::TimeDelta duration) = 0;
   virtual void AddBeginMainFrameQueueDurationNotCriticalDuration(
@@ -199,9 +199,9 @@ class RendererUMAReporter : public CompositorTimingHistory::UMAReporter {
         "Scheduling.Renderer.MainAndImplFrameTimeDelta", delta);
   }
 
-  void AddBeginMainFrameLatency(base::TimeDelta delta) override {
+  void AddBeginImplFrameLatency(base::TimeDelta delta) override {

[brianderson, 2017/03/16 19:11:56]

Nit: Here and below, can you put the method in the same order as the UMARporter
base class?

[stanisc, 2017/03/16 20:45:48]

Done.

     UMA_HISTOGRAM_CUSTOM_TIMES_DURATION(
-        "Scheduling.Renderer.VsyncToBeginMainFrameLatency", delta);
+        "Scheduling.Renderer.VsyncToBeginImplFrameLatency", delta);
   }
 };
 
@@ -281,9 +281,9 @@ class BrowserUMAReporter : public CompositorTimingHistory::UMAReporter {
         "Scheduling.Browser.MainAndImplFrameTimeDelta", delta);
   }
 
-  void AddBeginMainFrameLatency(base::TimeDelta delta) override {
+  void AddBeginImplFrameLatency(base::TimeDelta delta) override {
     UMA_HISTOGRAM_CUSTOM_TIMES_DURATION(
-        "Scheduling.Browser.VsyncToBeginMainFrameLatency", delta);
+        "Scheduling.Browser.VsyncToBeginImplFrameLatency", delta);
   }
 };
 
@@ -308,7 +308,7 @@ class NullUMAReporter : public CompositorTimingHistory::UMAReporter {
   void AddSubmitToAckLatency(base::TimeDelta duration) override {}
   void AddSubmitAckWasFast(bool was_fast) override {}
   void AddMainAndImplFrameTimeDelta(base::TimeDelta delta) override {}
-  void AddBeginMainFrameLatency(base::TimeDelta delta) override {}
+  void AddBeginImplFrameLatency(base::TimeDelta delta) override {}
 };
 
 }  // namespace
@@ -467,13 +467,18 @@ void CompositorTimingHistory::DidCreateAndInitializeCompositorFrameSink() {
 }
 
 void CompositorTimingHistory::WillBeginImplFrame(
-    bool new_active_tree_is_likely) {
+    bool new_active_tree_is_likely,
+    base::TimeTicks frame_time,
+    BeginFrameArgs::BeginFrameArgsType frame_type) {
   // The check for whether a BeginMainFrame was sent anytime between two
   // BeginImplFrames protects us from not detecting a fast main thread that
   // does all it's work and goes idle in between BeginImplFrames.
   // For example, this may happen if an animation is being driven with
   // setInterval(17) or if input events just happen to arrive in the
   // middle of every frame.
+  if (frame_type == BeginFrameArgs::NORMAL)
+    uma_reporter_->AddBeginImplFrameLatency(Now() - frame_time);
+
   if (!new_active_tree_is_likely && !did_send_begin_main_frame_) {
     SetBeginMainFrameNeededContinuously(false);
     SetBeginMainFrameCommittingContinuously(false);
@@ -504,8 +509,7 @@ void CompositorTimingHistory::BeginImplFrameNotExpectedSoon() {
 
 void CompositorTimingHistory::WillBeginMainFrame(
     bool on_critical_path,
-    base::TimeTicks main_frame_time,
-    BeginFrameArgs::BeginFrameArgsType frame_type) {
+    base::TimeTicks main_frame_time) {
   DCHECK_EQ(base::TimeTicks(), begin_main_frame_sent_time_);
   DCHECK_EQ(base::TimeTicks(), begin_main_frame_frame_time_);
 
@@ -513,11 +517,6 @@ void CompositorTimingHistory::WillBeginMainFrame(
   begin_main_frame_sent_time_ = Now();
   begin_main_frame_frame_time_ = main_frame_time;
 
-  if (frame_type == BeginFrameArgs::NORMAL) {
-    uma_reporter_->AddBeginMainFrameLatency(begin_main_frame_sent_time_ -
-                                            begin_main_frame_frame_time_);
-  }
-
   did_send_begin_main_frame_ = true;
   SetBeginMainFrameNeededContinuously(true);
 }