Implement autoplay gesture override experiment.

Source/core/html/HTMLMediaElement.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 282 matching lines @@
 
     void didMoveToNewDocument(Document& oldDocument) override;
 
     enum DisplayMode { Unknown, Poster, Video };
     DisplayMode displayMode() const { return m_displayMode; }
     virtual void setDisplayMode(DisplayMode mode) { m_displayMode = mode; }
 
     void setControllerInternal(MediaController*);
 
 private:
+    // These values are used for a histogram. Do not reorder.
+    enum AutoplayMetrics {
+        // Media element with autoplay seen.
+        AutoplayMediaFound = 0,
+        // Autoplay enabled and user stopped media play at any point.
+        AutoplayStopped = 1,
+        // Autoplay enabled but user bailed out on media play early.
+        AutoplayBailout = 2,
+        // Autoplay disabled but user manually started media.
+        AutoplayManualStart = 3,
+        // Autoplay was (re)enabled through a user-gesture triggered load()
+        AutoplayEnabledThroughLoad = 4,
+        // Autoplay disabled by sandbox flags.
+        AutoplayDisabledBySandbox = 5,
+        // AutoplayStopped for a media play that was started by the experiment.
+        AutoplayExperimentStopped = 6,
+        // AutoplayBailout for media a play that was started by the experiment.
+        AutoplayExperimentBailout = 7,
+        // Autoplay started by experiment when media scrolled into view.  We don't
+        // record whether it was a javascript or attribute autoplay request.
+        AutoplayExperimentStartedByScroll = 8,
+        // Autoplay started by experiment during initial load.
+        AutoplayExperimentStartedByLoad = 9,
+        // Autoplay started by experiment in play() call.
+        AutoplayExperimentStartedByPlay = 10,
+        // This enum value must be last.
+        NumberOfAutoplayMetrics,
+    };
+
     void createMediaPlayer();
 
     bool alwaysCreateUserAgentShadowRoot() const final { return true; }
     bool areAuthorShadowsAllowed() const final { return false; }
 
     bool supportsFocus() const final;
     bool isMouseFocusable() const final;
     bool layoutObjectIsNeeded(const ComputedStyle&) override;
     LayoutObject* createLayoutObject(const ComputedStyle&) override;
     InsertionNotificationRequest insertedInto(ContainerNode*) final;
@@ skipping 109 matching lines @@
 
     void changeNetworkStateFromLoadingToIdle();
 
     const AtomicString& mediaGroup() const;
     void setMediaGroup(const AtomicString&);
     void updateMediaController();
     bool isBlocked() const;
     bool isBlockedOnMediaController() const;
     bool isAutoplaying() const { return m_autoplaying; }
 
+    void recordAutoplayMetric(AutoplayMetrics);
+
+    // vvvv Helpers for clank autoplay investigation vvvv
+
+    // Install a scroll listener to check for changes in visibility.  If a
+    // listener is already installed, then this does nothing.
+    void autoplayExperimentInstallScrollListenerIfNeeded();
+
+    // Remove any scroll listener.  It's okay to call this if one isn't
+    // installed already.
+    void autoplayExperimentClearScrollListenerIfNeeded();
+
+    // Return true if any only if this player meets (most) of the eligibility
+    // requirements for the experiment to override the need for a user
+    // gesture.  This includes everything except the visibility test.
+    bool autoplayExperimentIsEligible() const;
+
+    // Return true if and only if the player is visible.
+    bool autoplayExperimentIsVisible();
+
+    // Set the mute flag on the media if we're in an experiment mode that
+    // requires it, else do nothing.
+    void autoplayExperimentMuteIfNeeded();
+
+    // In response to a scroll event, maybe start playing.  Returns true if
+    // only if it starts playback.
+    bool autoplayExperimentMaybeStartPlaying();
+
+    // Configure internal state to record that the autoplay experiment is
+    // going to start playback.  This doesn't actually start playback, since
+    // there are several different cases.
+    void autoplayExperimentPrepareToPlay(AutoplayMetrics);
+
+    // ^^^^ Helpers for clank autoplay investigation ^^^^
+
     WebMediaPlayer::CORSMode corsMode() const;
 
     // Returns the "direction of playback" value as specified in the HTML5 spec.
     enum DirectionOfPlayback { Backward, Forward };
     DirectionOfPlayback directionOfPlayback() const;
 
     // Returns the "effective playback rate" value as specified in the HTML5 spec.
     double effectivePlaybackRate() const;
 
     // Creates placeholder AudioTrack and/or VideoTrack objects when WebMemediaPlayer objects
@@ skipping 103 matching lines @@
 
     bool m_tracksAreReady : 1;
     bool m_haveVisibleTextTrack : 1;
     bool m_processingPreferenceChange : 1;
     bool m_remoteRoutesAvailable : 1;
     bool m_playingRemotely : 1;
     bool m_isFinalizing : 1;
     bool m_initialPlayWithoutUserGestures : 1;
     bool m_autoplayMediaCounted : 1;
 
+    // Autoplay experiment state.
+    // True if we've received a play() without a pause().
+    bool m_autoplayExperimentPlayPending : 1;
+
+    // Autoplay experiment state.
+    // True if and only if we initiated playback because of the autoplay
+    // experiment.  Once set, this is never unset.
+    bool m_autoplayExperimentStartedByExperiment : 1;
+
+    // Autoplay experiment state.
+    // Scroll listener for the autoplay experiment.
+    class AutoplayExperimentScrollListener;
+    friend class AutoplayExperimentScrollListener;
+    RefPtrWillBeMember<EventListener> m_autoplayExperimentScrollListener;
+
+    enum AutoplayExperimentMode {
+        ExperimentOff,
+        ExperimentAlways,
+        ExperimentIfMuted,
+        ExperimentPlayMuted
+    };
+    AutoplayExperimentMode m_autoplayExperimentMode;
+
     RefPtrWillBeMember<AudioTrackList> m_audioTracks;
     RefPtrWillBeMember<VideoTrackList> m_videoTracks;
     RefPtrWillBeMember<TextTrackList> m_textTracks;
     WillBeHeapVector<RefPtrWillBeMember<TextTrack>> m_textTracksWhenResourceSelectionBegan;
 
     OwnPtrWillBeMember<CueTimeline> m_cueTimeline;
 
 #if ENABLE(WEB_AUDIO)
     // This is a weak reference, since m_audioSourceNode holds a reference to us.
     // FIXME: Oilpan: Consider making this a strongly traced pointer with oilpan where strong cycles are not a problem.
     GC_PLUGIN_IGNORE("http://crbug.com/404577")
     RawPtrWillBeWeakMember<AudioSourceProviderClient> m_audioSourceNode;
 #endif
 
     friend class MediaController;
     PersistentWillBeMember<MediaController> m_mediaController;
+    friend class MyScrollListener;

[philipj_slow, 2015/07/21 12:51:29]

MyScrollListener is nowhere to be found?

[liberato (no reviews please), 2015/07/27 06:03:09]

that was sloppy of me.  thanks.

 
     friend class Internals;
     friend class TrackDisplayUpdateScope;
 
     static URLRegistry* s_mediaStreamRegistry;
 };
 
 inline bool isHTMLMediaElement(const HTMLElement& element)
 {
     return isHTMLAudioElement(element) || isHTMLVideoElement(element);
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLMediaElement);
 
 } // namespace blink
 
 #endif // HTMLMediaElement_h