Include viewport visibility checks for autoplay experiment.

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

Index: third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h
diff --git a/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h b/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h
index c9d015f062bce1126923f2ec3613ad7067c92219..ed3d75d178bc257d683449390db4ffbc3e5abf59 100644
--- a/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h
+++ b/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h
@@ -79,12 +79,56 @@ public:
     void mutedChanged();
     void positionChanged();
 
+    // For testing.
+    void triggerAutoplayViewportCheck();
+
 private:
+    // The location and size of our element, and the viewport.
+    class LocationState {
+    public:
+        LocationState() {}
+        LocationState(Element&);
+
+        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 element is visible.
+        bool isElementVisible() const;
+
+        // Return true if and only if the element's page is visible.
+        bool isPageVisible() const;
+
+    private:
+        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 element described by LocationState is
+    // not visible, and we care that it must be visible.
+    bool meetsVisibilityRequirements(const LocationState&) const;
+
+    // Return false if and only if m_element is not visible, and we care
+    // that it must be visible.  This is equivalent to calling
+    // meetsVisibilityRequirements(LocationState(m_element))
+    bool meetsVisibilityRequirements() const;
+
     // Set the muted flag on the media if we're in an experiment mode that
     // requires it, else do nothing.
     void muteIfNeeded();
@@ -98,6 +142,9 @@ private:
     // 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;
 
@@ -115,6 +162,20 @@ private:
     // 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_registeredWithLayoutObject : 1;
+
+    // According to our last position update, are we in the viewport?
+    bool m_wasInViewport : 1;
+
+    // According to our last position update, where was our element?
+    LocationState m_lastLocation;
+
+    // When was m_lastLocation set?
+    double m_lastLocationUpdateTime;
+
+    Timer<AutoplayExperimentHelper> m_viewportTimer;
+
     friend class Internals;
 };