[DevTools] Use device metrics emulation implemented in content.

Source/core/platform/ScrollbarThemeWin.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2008, 2009 Google Inc.
  *
  * 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
@@ skipping 15 matching lines @@
 
 #include "config.h"
 #include "core/platform/ScrollbarThemeWin.h"
 
 #include <windows.h>
 #include <vsstyle.h>
 
 #include "core/platform/LayoutTestSupport.h"
 #include "core/platform/PlatformMouseEvent.h"
 #include "core/platform/Scrollbar.h"
+#include "core/platform/ScrollbarThemeOverlay.h"
 #include "core/platform/graphics/GraphicsContext.h"
 #include "core/platform/win/SystemInfo.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebRect.h"
 #include "public/platform/win/WebThemeEngine.h"
 namespace WebCore {
 
 ScrollbarTheme* ScrollbarTheme::nativeTheme()
 {
+    if (RuntimeEnabledFeatures::overlayScrollbarsEnabled()) {
+        DEFINE_STATIC_LOCAL(ScrollbarThemeOverlay, theme, (7, 0, ScrollbarThemeOverlay::AllowHitTest));
+        return &theme;
+    }
+
     static ScrollbarThemeWin theme;
     return &theme;
 }
 
 // The scrollbar size in DumpRenderTree on the Mac - so we can match their
 // layout results. Entries are for regular, small, and mini scrollbars.
 // Metrics obtained using [NSScroller scrollerWidthForControlSize:]
 static const int kMacScrollbarSize[3] = { 15, 11, 15 };
 
 // Constants used to figure the drag rect outside which we should snap the
@@ skipping 191 matching lines @@
         int width = scrollbar->width() < 2 * girth ? scrollbar->width() / 2 : girth;
         return IntSize(width, thickness);
     }
 
     int height = scrollbar->height() < 2 * girth ? scrollbar->height() / 2 : girth;
     return IntSize(thickness, height);
 }
 
 
 } // namespace WebCore