Make compositor and blink talk in fractional scroll offset

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 12 matching lines @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WebLayer_h
 #define WebLayer_h
 
 #include "WebBlendMode.h"
 #include "WebColor.h"
 #include "WebCommon.h"
 #include "WebCompositorAnimation.h"
+#include "WebDoublePoint.h"
 #include "WebFloatPoint3D.h"
 #include "WebPoint.h"
 #include "WebRect.h"
 #include "WebSize.h"
 #include "WebString.h"
 #include "WebVector.h"
 
 class SkMatrix44;
 class SkImageFilter;
 
@@ skipping 111 matching lines @@
     // delta and offset even though it will not be a descendant of the scroll
     // in the layer hierarchy.
     virtual void setScrollParent(WebLayer*) = 0;
 
     // A layer will not respect any clips established by layers between it and
     // its nearest clipping ancestor. Note, the clip parent must be an ancestor.
     // This is not a requirement of the scroll parent.
     virtual void setClipParent(WebLayer*) = 0;
 
     // Scrolling
-    virtual void setScrollPosition(WebPoint) = 0;
-    virtual WebPoint scrollPosition() const = 0;
+    virtual void setScrollPositionDouble(WebDoublePoint) = 0;
+    virtual WebDoublePoint scrollPositionDouble() const = 0;
 
     // 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;
@@ skipping 31 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