[Video] Only start tracking foreground time if the video was resumed.

media/blink/video_frame_compositor.cc

Index: media/blink/video_frame_compositor.cc
diff --git a/media/blink/video_frame_compositor.cc b/media/blink/video_frame_compositor.cc
index 017bedc9ae9fc0b29b18e12c300790a24ca54f3b..c9cce634f81bfff10a56d23d1e3b5dc3ed0788dd 100644
--- a/media/blink/video_frame_compositor.cc
+++ b/media/blink/video_frame_compositor.cc
@@ -189,9 +189,12 @@ base::TimeDelta VideoFrameCompositor::GetCurrentFrameTimestamp() const {
   return current_frame_->timestamp();
 }
 
-void VideoFrameCompositor::SetForegroundTime(base::TimeTicks when) {
+void VideoFrameCompositor::SetForegroundTime(
+    base::TimeTicks when,
+    BackgroundVideoOptimization optimization) {

[DaleCurtis, 2017/01/18 23:39:01]

This is polluting VFC with knowledge about BackgroudnVideoOptimization. It seems
instead we should register a callback ala SetOnNextRenderedFrameCallback() or
similar. This cb can bind in the |when| value and record the histogram value
inside WMPI who has all this knowledge.

[whywhat, 2017/01/19 02:33:58]

Hm, ok. Will upload a follow up with this.

[whywhat, 2017/01/19 03:23:12]

Done. Looks neat to me :)

   DCHECK(compositor_task_runner_->BelongsToCurrentThread());
   foreground_time_ = when;
+  background_video_optimization_ = base::make_optional(optimization);
 }
 
 bool VideoFrameCompositor::ProcessNewFrame(
@@ -210,12 +213,21 @@ bool VideoFrameCompositor::ProcessNewFrame(
 
   current_frame_ = frame;
 
-  if (!foreground_time_.is_null()) {
+  if (!foreground_time_.is_null() && background_video_optimization_) {
     base::TimeDelta time_to_first_frame =
         base::TimeTicks::Now() - foreground_time_;
-    UMA_HISTOGRAM_TIMES("Media.Video.TimeFromForegroundToFirstFrame",
-                        time_to_first_frame);
+    if (background_video_optimization_.value() ==
+        BackgroundVideoOptimization::Paused) {
+      UMA_HISTOGRAM_TIMES("Media.Video.TimeFromForegroundToFirstFrame.Paused",
+                          time_to_first_frame);
+    } else if (background_video_optimization_.value() ==
+               BackgroundVideoOptimization::DisabledTrack) {
+      UMA_HISTOGRAM_TIMES(
+          "Media.Video.TimeFromForegroundToFirstFrame.DisableTrack",
+          time_to_first_frame);
+    }
     foreground_time_ = base::TimeTicks();
+    background_video_optimization_.reset();
   }
 
   return true;