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

content/renderer/render_view_impl.h

Index: content/renderer/render_view_impl.h
diff --git a/content/renderer/render_view_impl.h b/content/renderer/render_view_impl.h
index b28904316284ab52cca3c9d1210cf1fd767a1e62..453e8674a335985b7c6224f98ebc9069b227b473 100644
--- a/content/renderer/render_view_impl.h
+++ b/content/renderer/render_view_impl.h
@@ -730,13 +730,6 @@ class CONTENT_EXPORT RenderViewImpl
     navigation_gesture_ = gesture;
   }
 
-  // Platform specific theme preferences if any are updated here.
-#if defined(OS_WIN)
-  void UpdateThemePrefs();
-#else
-  void UpdateThemePrefs() {}
-#endif
-
   void UpdateWebViewWithDeviceScaleFactor();
 
   // ---------------------------------------------------------------------------