Refactor wheel event handler registration in ScrollingCoordinator

public/platform/WebLayer.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 165 matching lines @@
     // To set a WebLayer as scrollable we must specify the corresponding clip layer.
     virtual void setScrollClipLayer(WebLayer*) = 0;
     virtual bool scrollable() const = 0;
     virtual void setUserScrollable(bool horizontal, bool vertical) = 0;
     virtual bool userScrollableHorizontal() const = 0;
     virtual bool userScrollableVertical() const = 0;
 
     virtual void setHaveWheelEventHandlers(bool) = 0;
     virtual bool haveWheelEventHandlers() const = 0;
 
+    virtual void setHaveScrollEventHandlers(bool) = 0;
+    virtual bool haveScrollEventHandlers() const = 0;
+
     virtual void setShouldScrollOnMainThread(bool) = 0;
     virtual bool shouldScrollOnMainThread() const = 0;
 
     virtual void setNonFastScrollableRegion(const WebVector<WebRect>&) = 0;
     virtual WebVector<WebRect> nonFastScrollableRegion() const = 0;
 
     virtual void setTouchEventHandlerRegion(const WebVector<WebRect>&) = 0;
     virtual WebVector<WebRect> touchEventHandlerRegion() const = 0;
 
     virtual void setIsContainerForFixedPositionLayers(bool) = 0;
@@ skipping 17 matching lines @@
 
     // True if the layer is not part of a tree attached to a WebLayerTreeView.
     virtual bool isOrphan() const = 0;
 
     virtual void setWebLayerClient(WebLayerClient*) = 0;
 };
 
 } // namespace blink
 
 #endif // WebLayer_h