Fix scrollbar buttons at hidpi when enable-use-zoom-for-dsf is on.

content/renderer/render_view_impl.h

 // Copyright (c) 2012 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_RENDERER_RENDER_VIEW_IMPL_H_
 #define CONTENT_RENDERER_RENDER_VIEW_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 744 matching lines @@
   // this object.
   base::ObserverList<RenderViewObserver>& observers() { return observers_; }
 
   NavigationGesture navigation_gesture() {
     return navigation_gesture_;
   }
   void set_navigation_gesture(NavigationGesture gesture) {
     navigation_gesture_ = gesture;
   }
 
-  // Platform specific theme preferences if any are updated here.
-#if defined(OS_WIN)
-  void UpdateThemePrefs();
-#else
-  void UpdateThemePrefs() {}
-#endif
-
   void UpdateWebViewWithDeviceScaleFactor();
 
   // ---------------------------------------------------------------------------
   // ADDING NEW FUNCTIONS? Please keep private functions alphabetized and put
   // it in the same order in the .cc file as it was in the header.
   // ---------------------------------------------------------------------------
 
   // Settings ------------------------------------------------------------------
 
   WebPreferences webkit_preferences_;
@@ skipping 233 matching lines @@
   // use the Observer interface to filter IPC messages and receive frame change
   // notifications.
   // ---------------------------------------------------------------------------
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_VIEW_IMPL_H_