Avoid calling the GetSystemMetrics API in the renderer process on Windows to get the scrollbar metr…

content/child/webthemeengine_impl_default.h

 // Copyright 2014 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 CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_
 #define CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_
 
 #include "third_party/WebKit/public/platform/WebThemeEngine.h"
 
 namespace content {
 
 class WebThemeEngineImpl : public blink::WebThemeEngine {
  public:
   // WebThemeEngine methods:
   virtual blink::WebSize getSize(blink::WebThemeEngine::Part);
   virtual void paint(
       blink::WebCanvas* canvas,
       blink::WebThemeEngine::Part part,
       blink::WebThemeEngine::State state,
       const blink::WebRect& rect,
       const blink::WebThemeEngine::ExtraParams* extra_params);
   virtual void paintStateTransition(blink::WebCanvas* canvas,
                                     blink::WebThemeEngine::Part part,
                                     blink::WebThemeEngine::State startState,
                                     blink::WebThemeEngine::State endState,
                                     double progress,
                                     const blink::WebRect& rect);
+
+  // The next 4 functions are only invoked on Windows.

[jam, 2015/04/03 15:08:19]

why not behind OS_WIN?

[ananta, 2015/04/03 19:17:04]

Done.

+
+  // Caches the vertical scrollbar width.
+  static void SetVerticalScrollbarWidth(int32 vertical_scroll_bar_width);
+
+  // Caches the horizontal scrollbar height.
+  static void SetHorizontalScrollbarHeight(int32 horizontal_scroll_bar_height);
+
+  // Caches the vertical scrollbar arrow bitmap.
+  static void SetVerticalArrowBitmapHeight(int32 vertical_arrow_bitmap_height);
+
+  // Caches the horizontal scrollbar arrow bitmap.
+  static void SetHorizontalArrowBitmapWidth(int32 horizontal_arrow_bitmap_width);

[jam, 2015/04/03 15:08:19]

nit 80 chars

[ananta, 2015/04/03 19:17:04]

The four functions here have been collapsed to one function
CacheScrollBarMetrics.

+
+ private:
+  // The width of a vertical scroll bar in dips.
+  static int32 vertical_scroll_bar_width_;

[jam, 2015/04/03 15:08:19]

nit: i think the convention is to put these as globals in an anonymous
namespace?

[ananta, 2015/04/03 19:17:04]

Done.

+
+  // The height of a horizontal scroll bar in dips.
+  static int32 horizontal_scroll_bar_height_;
+
+  // The height of the arrow bitmap on a vertical scroll bar in dips.
+  static int32 vertical_arrow_bitmap_height_;
+
+  // The width of the arrow bitmap on a horizontal scroll bar in dips.
+  static int32 horizontal_arrow_bitmap_width_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WEBTHEMEENGINE_IMPL_DEFAULT_H_