Pass scroll bar placement as an enum instead of std::string

Source/platform/scroll/ScrollbarTheme.h

 /*
  * Copyright (C) 2008 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 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef ScrollbarTheme_h
 #define ScrollbarTheme_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/IntRect.h"
 #include "platform/graphics/paint/DisplayItem.h"
 #include "platform/scroll/ScrollTypes.h"
+#include "public/platform/mac/MacScrollTypes.h"
 
 namespace blink {
 
 class GraphicsContext;
 class PlatformMouseEvent;
 class ScrollbarThemeClient;
 
 class PLATFORM_EXPORT ScrollbarTheme {
     WTF_MAKE_NONCOPYABLE(ScrollbarTheme); WTF_MAKE_FAST_ALLOCATED(ScrollbarTheme);
 public:
     ScrollbarTheme() { }
     virtual ~ScrollbarTheme() { }
 
     virtual void updateEnabledState(ScrollbarThemeClient*) { }
 
     virtual bool paint(ScrollbarThemeClient*, GraphicsContext*, const IntRect& damageRect);
 
     virtual ScrollbarPart hitTest(ScrollbarThemeClient*, const IntPoint&);
 
     virtual int scrollbarThickness(ScrollbarControlSize = RegularScrollbar) { return 0; }
     virtual int scrollbarMargin() const { return 0; }
 
-    virtual ScrollbarButtonsPlacement buttonsPlacement() const { return ScrollbarButtonsSingle; }
+    virtual ScrollbarButtonsPlacement buttonsPlacement() const { return ScrollbarButtonsPlacementSingle; }
 
     virtual bool supportsControlTints() const { return false; }
     virtual bool usesOverlayScrollbars() const { return false; }
     virtual void updateScrollbarOverlayStyle(ScrollbarThemeClient*) { }
 
     virtual bool invalidateOnMouseEnterExit() { return false; }
 
     void invalidateParts(ScrollbarThemeClient* scrollbar, ScrollbarControlPartMask mask)
     {
         if (mask & BackButtonStartPart)
@@ skipping 70 matching lines @@
     static DisplayItem::Type buttonPartToDisplayItemType(ScrollbarPart);
     static DisplayItem::Type trackPiecePartToDisplayItemType(ScrollbarPart);
 
 private:
     static ScrollbarTheme* nativeTheme(); // Must be implemented to return the correct theme subclass.
     static bool gMockScrollbarsEnabled;
 };
 
 }
 #endif