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

Source/web/PinchViewports.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 52 matching lines @@
     , m_overlayScrollbarHorizontal(GraphicsLayer::create(m_owner->graphicsLayerFactory(), this))
     , m_overlayScrollbarVertical(GraphicsLayer::create(m_owner->graphicsLayerFactory(), this))
 {
     m_innerViewportContainerLayer->platformLayer()->setIsContainerForFixedPositionLayers(true);
     // No need for the inner viewport to clip, since the compositing
     // surface takes care of it -- and clipping here would interfere with
     // dynamically-sized viewports on Android.
     m_innerViewportContainerLayer->setMasksToBounds(false);
 
     m_innerViewportScrollLayer->platformLayer()->setScrollable(true);
+    m_innerViewportScrollLayer->platformLayer()->setUserScrollable(true, true);
 
     m_innerViewportContainerLayer->addChild(m_pageScaleLayer.get());
     m_pageScaleLayer->addChild(m_innerViewportScrollLayer.get());
     m_innerViewportContainerLayer->addChild(m_overlayScrollbarHorizontal.get());
     m_innerViewportContainerLayer->addChild(m_overlayScrollbarVertical.get());
 
     // Setup the inner viewport overlay scrollbars.
     setupScrollbar(WebScrollbar::Horizontal);
     setupScrollbar(WebScrollbar::Vertical);
 }
@@ skipping 123 matching lines @@
     } else if (graphicsLayer == m_overlayScrollbarVertical.get()) {
         name =  "Overlay Scrollbar Vertical Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebKit