scroll: Tell the platform layer whether it can be scrolled by the user.

Source/core/page/scrolling/ScrollingCoordinator.cpp

 /*
  * Copyright (C) 2011 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 304 matching lines @@
     if (scrollLayer) {
         bool isMainFrame = isForMainFrame(scrollableArea);
         scrollLayer->setScrollableArea(scrollableArea, isMainFrame);
     }
 
     WebLayer* webLayer = scrollingWebLayerForScrollableArea(scrollableArea);
     if (webLayer) {
         webLayer->setScrollable(true);
         webLayer->setScrollPosition(IntPoint(scrollableArea->scrollPosition() - scrollableArea->minimumScrollPosition()));
         webLayer->setMaxScrollPosition(IntSize(scrollableArea->scrollSize(HorizontalScrollbar), scrollableArea->scrollSize(VerticalScrollbar)));
+        bool canScrollX = scrollableArea->userInputScrollable(HorizontalScrollbar);
+        bool canScrollY = scrollableArea->userInputScrollable(VerticalScrollbar);
+        webLayer->setUserScrollable(canScrollX, canScrollY);
     }
     if (WebScrollbarLayer* scrollbarLayer = getWebScrollbarLayer(scrollableArea, HorizontalScrollbar)) {
         GraphicsLayer* horizontalScrollbarLayer = horizontalScrollbarLayerForScrollableArea(scrollableArea);
         if (horizontalScrollbarLayer)
             setupScrollbarLayer(horizontalScrollbarLayer, scrollbarLayer, webLayer);
     }
     if (WebScrollbarLayer* scrollbarLayer = getWebScrollbarLayer(scrollableArea, VerticalScrollbar)) {
         GraphicsLayer* verticalScrollbarLayer = verticalScrollbarLayerForScrollableArea(scrollableArea);
         if (verticalScrollbarLayer)
             setupScrollbarLayer(verticalScrollbarLayer, scrollbarLayer, webLayer);
@@ skipping 524 matching lines @@
         stringBuilder.resize(stringBuilder.length() - 2);
     return stringBuilder.toString();
 }
 
 String ScrollingCoordinator::mainThreadScrollingReasonsAsText() const
 {
     return mainThreadScrollingReasonsAsText(mainThreadScrollingReasons());
 }
 
 } // namespace WebCore