Add ScrollDirectionPhysical enum in Scroll types.

Source/platform/scroll/ScrollableArea.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  * Copyright (C) 2008, 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 104 matching lines @@
         m_scrollOrigin = origin;
         m_scrollOriginChanged = true;
     }
 }
 
 GraphicsLayer* ScrollableArea::layerForContainer() const
 {
     return layerForScrolling() ? layerForScrolling()->parent() : 0;
 }
 
-bool ScrollableArea::scroll(ScrollDirection direction, ScrollGranularity granularity, float delta)
+bool ScrollableArea::scroll(ScrollDirectionPhysical direction, ScrollGranularity granularity, float delta)
 {
-    ASSERT(!isLogical(direction));
-
     ScrollbarOrientation orientation;
     if (direction == ScrollUp || direction == ScrollDown)
         orientation = VerticalScrollbar;
     else
         orientation = HorizontalScrollbar;
 
     if (!userInputScrollable(orientation))
         return false;
 
     cancelProgrammaticScrollAnimation();
@@ skipping 443 matching lines @@
 {
     return scrollSize(orientation);
 }
 
 float ScrollableArea::pixelStep(ScrollbarOrientation) const
 {
     return 1;
 }
 
 } // namespace blink