Record the offscreen playing duration of autoplaying muted videos

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 282b0fae379e98ae19c87e05ddba06d8669e3091..fd3a02cb8e6b89a5fd73ef90f6e6f64cd0d2b918 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
@@ -493,6 +493,7 @@ private:
     EnumerationHistogram& showControlsHistogram() const;
 
     void recordAutoplaySourceMetric(int source);
+    void recordAutoplayVideoOffscreenMetric(double timeDeltaMS);
 
     void onVisibilityChangedForAutoplay(bool isVisible);
 
@@ -612,6 +613,18 @@ private:
     GC_PLUGIN_IGNORE("http://crbug.com/404577")
     WeakMember<AudioSourceProviderClient> m_audioSourceNode;
 
+    // Variables used for recording the duration of autoplay muted video playing offscreen.
+    // The variables are valid when |m_autoplayOffscrenVisibilityObserver| is non-null. Whenever the playback pauses, the UMA is recorded, and |m_autoplayOffscreenVisibilityObserver| is set to null.
+    double m_mutedVideoAutoplayStartTimeMS;
+    double m_mutedVideoAutoplayOffscreenDurationMS;
+    bool m_isVisible;
+    bool m_isAutoplayFromAttribute;
+    Member<ElementVisibilityObserver> m_autoplayOffscreenVisibilityObserver;
+
+    void maybeRecordMutedVideoAutoplayOffscreenDuration();
+
+    void onVisibilityChangedForAutoplayOffscreen(bool isVisibile);
+
     // AudioClientImpl wraps an AudioSourceProviderClient.
     // When the audio format is known, Chromium calls setFormat().
     class AudioClientImpl final : public GarbageCollectedFinalized<AudioClientImpl>, public WebAudioSourceProviderClient {