Implement top controls show/hide functionality for main thread scrolling

public/platform/WebLayerTreeView.h

 /*
  * Copyright (C) 2011 Google 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
@@ skipping 14 matching lines @@
 
 #ifndef WebLayerTreeView_h
 #define WebLayerTreeView_h
 
 #include "WebColor.h"
 #include "WebCommon.h"
 #include "WebFloatPoint.h"
 #include "WebNonCopyable.h"
 #include "WebPrivateOwnPtr.h"
 #include "WebSize.h"
+#include "WebTopControlsState.h"
 
 class SkBitmap;
 
 namespace blink {
 
 class WebCompositeAndReadbackAsyncCallback;
 class WebLayer;
 struct WebPoint;
 struct WebSelectionBound;
+class WebWidget;
 
 class WebLayerTreeView {
 public:
     virtual ~WebLayerTreeView() { }
 
     // Initialization and lifecycle --------------------------------------
 
     // Sets the root of the tree. The root is set by way of the constructor.
     virtual void setRootLayer(const WebLayer&) = 0;
     virtual void clearRootLayer() = 0;
@@ skipping 25 matching lines @@
     // If useAnchor is true, destination is a point on the screen that will remain fixed for the duration of the animation.
     // If useAnchor is false, destination is the final top-left scroll position.
     virtual void startPageScaleAnimation(const WebPoint& destination, bool useAnchor, float newPageScale, double durationSec) = 0;
 
     virtual void heuristicsForGpuRasterizationUpdated(bool) { }
 
     // Sets the amount that the top controls are showing, from 0 (hidden) to 1
     // (fully shown).
     virtual void setTopControlsShownRatio(float) { }
 
+    // Update top controls permitted and current states
+    virtual void updateTopControlsState(WebTopControlsState constraints, WebTopControlsState current, bool animate) { }
+
+    // Set top controls height. If |shrinkViewport| is set to true, then Blink shrunk the viewport clip
+    // layers by the top controls height.
+    virtual void setTopControlsHeight(float height, bool shrinkViewport) { }
+
     // Flow control and scheduling ---------------------------------------
 
     // Indicates that an animation needs to be updated.
     virtual void setNeedsAnimate() = 0;
 
     // Indicates whether a commit is pending.
     virtual bool commitRequested() const = 0;
 
     // Relays the end of a fling animation.
     virtual void didStopFlinging() { }
@@ skipping 42 matching lines @@
     // Toggles continuous painting
     virtual void setContinuousPaintingEnabled(bool) { }
 
     // Toggles scroll bottleneck rects on the HUD layer
     virtual void setShowScrollBottleneckRects(bool) { }
 };
 
 } // namespace blink
 
 #endif // WebLayerTreeView_h