Implement autoplay gesture override experiment.

Source/core/layout/LayoutView.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 24 matching lines @@
 #include "platform/PODFreeListArena.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/heap/Handle.h"
 #include "platform/scroll/ScrollableArea.h"
 #include "wtf/OwnPtr.h"
 
 namespace blink {
 
 class DeprecatedPaintLayerCompositor;
 class LayoutQuote;
+class LayoutMedia;
 
 // The root of the layout tree, corresponding to the CSS initial containing block.
 // It's dimensions match that of the logical viewport (which may be different from
 // the visible viewport in fixed-layout mode), and it is always at position (0,0)
 // relative to the document (and so isn't necessarily in view).
 class CORE_EXPORT LayoutView final : public LayoutBlockFlow {
 public:
     explicit LayoutView(Document*);
     ~LayoutView() override;
     void willBeDestroyed() override;
@@ skipping 127 matching lines @@
     void pushLayoutState(LayoutState& layoutState) { m_layoutState = &layoutState; }
     void popLayoutState() { ASSERT(m_layoutState); m_layoutState = m_layoutState->next(); }
     void invalidateTreeIfNeeded(PaintInvalidationState&) final;
 
     LayoutRect visualOverflowRect() const override;
 
     // Invalidates paint for the entire view, including composited descendants, but not including child frames.
     // It is very likely you do not want to call this method.
     void setShouldDoFullPaintInvalidationForViewAndAllDescendants();
 
+    // Some LayoutMedias want to know about their viewport visibility for
+    // crbug.com/487345,402044 .  This facility will be removed once those
+    // experiments complete.
+    void registerMediaForPositionChangeNotification(LayoutMedia*);
+    void unregisterMediaForPositionChangeNotification(LayoutMedia*);
+    // Notify all registered LayoutMedias that their position on-screen might
+    // have changed.
+    void sendMediaPositionChangeNotifications();
+
 private:
     void mapLocalToContainer(const LayoutBoxModelObject* paintInvalidationContainer, TransformState&, MapCoordinatesFlags = ApplyContainerFlip, bool* wasFixed = nullptr, const PaintInvalidationState* = nullptr) const override;
 
     template <typename Strategy>
     void commitPendingSelectionAlgorithm();
 
     const LayoutObject* pushMappingToContainer(const LayoutBoxModelObject* ancestorToStopAt, LayoutGeometryMap&) const override;
     void mapAbsoluteToLocalPoint(MapCoordinatesFlags, TransformState&) const override;
     void computeSelfHitTestRects(Vector<LayoutRect>&, const LayoutPoint& layerOffset) const override;
 
@@ skipping 25 matching lines @@
     RefPtr<IntervalArena> m_intervalArena;
 
     LayoutQuote* m_layoutQuoteHead;
     unsigned m_layoutCounterCount;
 
     unsigned m_hitTestCount;
     unsigned m_hitTestCacheHits;
     OwnPtrWillBePersistent<HitTestCache> m_hitTestCache;
 
     OwnPtrWillBePersistent<PendingSelection> m_pendingSelection;
+
+    Vector<LayoutMedia*> m_mediaForPositionNotification;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutView, isLayoutView());
 
 // Suspends the PaintInvalidationState cached offset and clipRect optimization. Used under transforms
 // that cannot be represented by PaintInvalidationState (common in SVG) and when paint invalidation
 // containers don't follow the common tree-walk algorithm (e.g. when an absolute positioned descendant
 // is nested under a relatively positioned inline-block child).
 class ForceHorriblySlowRectMapping {
     STACK_ALLOCATED();
@@ skipping 13 matching lines @@
             m_paintInvalidationState->m_cachedOffsetsEnabled = true;
     }
 private:
     const PaintInvalidationState* m_paintInvalidationState;
     bool m_didDisable;
 };
 
 } // namespace blink
 
 #endif // LayoutView_h