Split NativeThemeAura into Overlay and NonOverlay versions.

ui/native_theme/native_theme.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 UI_NATIVE_THEME_NATIVE_THEME_H_
 #define UI_NATIVE_THEME_NATIVE_THEME_H_
 
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "build/build_config.h"
@@ skipping 343 matching lines @@
 
   // Return a color from the system theme.
   virtual SkColor GetSystemColor(ColorId color_id) const = 0;
 
   // Returns a shared instance of the native theme that should be used for web
   // rendering. Do not use it in a normal application context (i.e. browser).
   // The returned object should not be deleted by the caller. This function is
   // not thread safe and should only be called from the UI thread. Each port of
   // NativeTheme should provide its own implementation of this function,
   // returning the port's subclass.
-  static NativeTheme* GetInstanceForWeb();
+  static NativeTheme* GetInstanceForWeb(bool use_overlay_scrollbars);
 
   // Add or remove observers to be notified when the native theme changes.
   void AddObserver(NativeThemeObserver* observer);
   void RemoveObserver(NativeThemeObserver* observer);
 
   // Notify observers of native theme changes.
   void NotifyObservers();
 
  protected:
   NativeTheme();
   virtual ~NativeTheme();
 
   unsigned int thumb_inactive_color_;
   unsigned int thumb_active_color_;
   unsigned int track_color_;
 
  private:
   // Observers to notify when the native theme changes.
   base::ObserverList<NativeThemeObserver> native_theme_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeTheme);
 };
 
 }  // namespace ui
 
 #endif  // UI_NATIVE_THEME_NATIVE_THEME_H_