When autoplaying muted video, record when unmute happen and the result.

third_party/WebKit/Source/core/html/HTMLMediaElement.h

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.h b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
index f42f1eb01b3c50a65d583be29b68c2d15e169b4d..855cabba4fa8d4c26e329b98bd828d5be11f39cb 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
@@ -298,6 +298,8 @@ protected:
     void recordAutoplayMetric(AutoplayMetrics);
 
 private:
+    enum class AutoplayUnmuteStatus { Failure, Success };

[whywhat, 2016/06/28 10:20:59]

nit: do we really need two enums for this? this one could be a bool with the
method named recordAutoplayUnmutePausedState(bool paused) ?

Then the recordXX method would look like:

autoplayUnmuteHistogram.count(paused ? AutoplayUnmuteActionFailure :
AutoplayUnmuteActionSuccess);

[mlamouri (slow - plz ping), 2016/06/28 13:58:27]

I moved to one enum in the header used for histograms too.

+
     void resetMediaPlayerAndMediaSource();
 
     bool alwaysCreateUserAgentShadowRoot() const final { return true; }
@@ -492,6 +494,7 @@ private:
     EnumerationHistogram& showControlsHistogram() const;
 
     void recordAutoplaySourceMetric(int source);
+    void recordAutoplayUnmuteStatus(AutoplayUnmuteStatus);
 
     void onVisibilityChangedForAutoplay(bool isVisible);