Add ScrollDirectionPhysical enum in Scroll types.

Source/core/frame/RootFrameViewport.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef RootFrameViewport_h
 #define RootFrameViewport_h
 
 #include "core/CoreExport.h"
 #include "platform/scroll/ScrollableArea.h"
 
@@ skipping 41 matching lines @@
     bool scrollbarsCanBeActive() const override;
     IntRect scrollableAreaBoundingBox() const override;
     bool userInputScrollable(ScrollbarOrientation) const override;
     bool shouldPlaceVerticalScrollbarOnLeft() const override;
     void invalidateScrollbarRect(Scrollbar*, const IntRect&) override;
     void invalidateScrollCornerRect(const IntRect&) override;
     GraphicsLayer* layerForContainer() const override;
     GraphicsLayer* layerForScrolling() const override;
     GraphicsLayer* layerForHorizontalScrollbar() const override;
     GraphicsLayer* layerForVerticalScrollbar() const override;
-    bool scroll(ScrollDirection, ScrollGranularity, float delta = 1) override;
+    bool scroll(ScrollDirectionPhysical, ScrollGranularity, float delta = 1) override;
     // TODO(bokan): This method should be removed. It should be replaced by
     // making EventHandler::handleWheelEvent unpack the WheelEvent and make a
     // call to this class' scroll method.
     ScrollResult handleWheel(const PlatformWheelEvent&) override;
 
 private:
     RootFrameViewport(ScrollableArea& visualViewport, ScrollableArea& layoutViewport);
 
     DoublePoint scrollOffsetFromScrollAnimators() const;
 
     // If either of the layout or visual viewports are scrolled explicitly (i.e. not
     // through this class), their updated offset will not be reflected in this class'
     // animator so use this method to pull updated values when necessary.
     void updateScrollAnimator();
 
     ScrollableArea& visualViewport() const { return m_visualViewport; }
     ScrollableArea& layoutViewport() const { return m_layoutViewport; }
 
     ScrollableArea& m_visualViewport;
     ScrollableArea& m_layoutViewport;
 };
 
 } // namespace blink
 
 #endif // RootFrameViewport_h