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

Source/core/layout/LayoutScrollbar.cpp

Index: Source/core/layout/LayoutScrollbar.cpp
diff --git a/Source/core/layout/LayoutScrollbar.cpp b/Source/core/layout/LayoutScrollbar.cpp
index 819c2754d66c3cc248b4753a622d3832eb87ca01..1829b789c01c9dcd836012414a8c8f9d67b8d81c 100644
--- a/Source/core/layout/LayoutScrollbar.cpp
+++ b/Source/core/layout/LayoutScrollbar.cpp
@@ -237,18 +237,18 @@ void LayoutScrollbar::updateScrollbarPart(ScrollbarPart partType, bool destroy)
         ScrollbarButtonsPlacement buttonsPlacement = theme()->buttonsPlacement();
         switch (partType) {
         case BackButtonStartPart:
-            needLayoutObject = (buttonsPlacement == ScrollbarButtonsSingle || buttonsPlacement == ScrollbarButtonsDoubleStart
-                || buttonsPlacement == ScrollbarButtonsDoubleBoth);
+            needLayoutObject = (buttonsPlacement == ScrollbarButtonsPlacementSingle || buttonsPlacement == ScrollbarButtonsPlacementDoubleStart
+                || buttonsPlacement == ScrollbarButtonsPlacementDoubleBoth);
             break;
         case ForwardButtonStartPart:
-            needLayoutObject = (buttonsPlacement == ScrollbarButtonsDoubleStart || buttonsPlacement == ScrollbarButtonsDoubleBoth);
+            needLayoutObject = (buttonsPlacement == ScrollbarButtonsPlacementDoubleStart || buttonsPlacement == ScrollbarButtonsPlacementDoubleBoth);
             break;
         case BackButtonEndPart:
-            needLayoutObject = (buttonsPlacement == ScrollbarButtonsDoubleEnd || buttonsPlacement == ScrollbarButtonsDoubleBoth);
+            needLayoutObject = (buttonsPlacement == ScrollbarButtonsPlacementDoubleEnd || buttonsPlacement == ScrollbarButtonsPlacementDoubleBoth);
             break;
         case ForwardButtonEndPart:
-            needLayoutObject = (buttonsPlacement == ScrollbarButtonsSingle || buttonsPlacement == ScrollbarButtonsDoubleEnd
-                || buttonsPlacement == ScrollbarButtonsDoubleBoth);
+            needLayoutObject = (buttonsPlacement == ScrollbarButtonsPlacementSingle || buttonsPlacement == ScrollbarButtonsPlacementDoubleEnd
+                || buttonsPlacement == ScrollbarButtonsPlacementDoubleBoth);
             break;
         default:
             break;