MacViews: Don't draw custom frame on Mac

chrome/browser/ui/views/frame/native_browser_frame.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 CHROME_BROWSER_UI_VIEWS_FRAME_NATIVE_BROWSER_FRAME_H_
 #define CHROME_BROWSER_UI_VIEWS_FRAME_NATIVE_BROWSER_FRAME_H_
 
 #include "ui/base/ui_base_types.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/views/widget/widget.h"
 
 class BrowserFrame;
 class BrowserView;
 
 namespace views {
 class NativeWidget;
 }
 
 class NativeBrowserFrame {
  public:
   virtual ~NativeBrowserFrame() {}
 
   // Returns the platform specific InitParams for initializing our widget.
   virtual views::Widget::InitParams GetWidgetParams() = 0;
 
+  // Returns |true| if we should use the custom frame.
+  virtual bool UseCustomFrame() const = 0;
+
   // Returns true if the OS takes care of showing the system menu. Returning
   // false means BrowserFrame handles showing the system menu.
   virtual bool UsesNativeSystemMenu() const = 0;
 
   // Returns true when the window placement should be stored.
   virtual bool ShouldSaveWindowPlacement() const = 0;
 
   // Retrieves the window placement (show state and bounds) for restoring.
   virtual void GetWindowPlacement(gfx::Rect* bounds,
                                   ui::WindowShowState* show_state) const = 0;
 
  protected:
   friend class BrowserFrame;
 
   // BrowserFrame pass-thrus ---------------------------------------------------
   // See browser_frame.h for documentation:
   virtual int GetMinimizeButtonOffset() const = 0;
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_FRAME_NATIVE_BROWSER_FRAME_H_