Add ScrollDirectionPhysical enum in Scroll types.

Source/platform/scroll/ScrollableArea.cpp

Index: Source/platform/scroll/ScrollableArea.cpp
diff --git a/Source/platform/scroll/ScrollableArea.cpp b/Source/platform/scroll/ScrollableArea.cpp
index c8d8d9f16f607a815cc15c5524ce773bf9ecd5fe..e0dfdf682c36ad9538de038860076a8507d899b3 100644
--- a/Source/platform/scroll/ScrollableArea.cpp
+++ b/Source/platform/scroll/ScrollableArea.cpp
@@ -122,10 +122,8 @@ 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;