Include viewport visibility checks for autoplay experiment.

Source/core/html/AutoplayExperimentHelper.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef AutoplayExperimentHelper_h
 #define AutoplayExperimentHelper_h
 
 #include "core/html/AutoplayExperimentConfig.h"
 #include "core/page/Page.h"
 #include "platform/Timer.h"
@@ skipping 61 matching lines @@
 public:
     AutoplayExperimentHelper(HTMLMediaElement&);
     ~AutoplayExperimentHelper();
 
     void becameReadyToPlay();
     void playMethodCalled();
     void pauseMethodCalled();
     void mutedChanged();
     void positionChanged();
 
+    // For testing.
+    void triggerAutoplayViewportCheck();
+
 private:
+    // The location and size of our element, and the viewport.  Also supports
+    // "not valid", in case some of the information isn't available.
+    class LocationState {
+    public:
+        LocationState() : m_valid(false) {}
+        LocationState(Element&);
+
+        bool valid() const { return m_valid; }
+        PageVisibilityState visibilityState() const { return m_visibilityState; }
+        const IntRect& element() const { return m_element; }
+        const IntRect& screen() const { return m_screen; }
+
+        bool operator==(const LocationState&) const;
+        bool operator!=(const LocationState&) const;
+
+        // Return true if and only if the player is visible.
+        bool isInViewport();
+
+    private:
+        bool m_valid;
+        PageVisibilityState m_visibilityState;
+        IntRect m_element;
+        IntRect m_screen;
+    };
+
+    // Register to receive position updates, if we haven't already.  If we
+    // have, then this does nothing.
+    void registerForPositionUpdatesIfNeeded();
+
+    // Un-register for position updates, if we are currently registered.
+    void unregisterForPositionUpdatesIfNeeded();
+
     // 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 isEligible() const;
 
+    // Return false if and only if the player is not visible, and we care
+    // that it must be visible.
+    bool isInViewportIfNeeded();
+
     // Set the muted flag on the media if we're in an experiment mode that
     // requires it, else do nothing.
     void muteIfNeeded();
 
     // Maybe override the requirement for a user gesture, and start playing
     // autoplay media.  Returns true if only if it starts playback.
     bool maybeStartPlaying();
 
     // 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 prepareToPlay(AutoplayMetrics);
 
+    // Process a timer for checking visibility.
+    void viewportTimerFired(Timer<AutoplayExperimentHelper>*);
+
     // Return our media element's document.
     Document& document() const;
 
     inline bool enabled(AutoplayExperimentConfig::Mode mode) const
     {
         return ((int)m_mode) & ((int)mode);
     }
 
 private:
     HTMLMediaElement& m_element;
 
     AutoplayExperimentConfig::Mode m_mode;
 
     // Autoplay experiment state.
     // True if we've received a play() without a pause().
     bool m_playPending : 1;
 
+    // Are we registered with the view for position updates?
+    bool m_registeredWithView : 1;
+
+    // According to our last position update, are we in the viewport?
+    bool m_wasInViewport : 1;
+
+    Timer<AutoplayExperimentHelper> m_viewportTimer;
+
     friend class Internals;
 };
 
 } // namespace blink
 
 #endif // AutoplayExperimentHelper_h