MacViews: Don't draw custom frame on Mac

chrome/browser/ui/views/frame/browser_frame_ash.h

 // Copyright 2013 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_BROWSER_FRAME_ASH_H_
 #define CHROME_BROWSER_UI_VIEWS_FRAME_BROWSER_FRAME_ASH_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/ui/views/frame/native_browser_frame.h"
@@ skipping 17 matching lines @@
 
   BrowserView* browser_view() const { return browser_view_; }
 
  protected:
   // Overridden from views::NativeWidgetAura:
   void OnWindowDestroying(aura::Window* window) override;
   void OnWindowTargetVisibilityChanged(bool visible) override;
 
   // Overridden from NativeBrowserFrame:
   views::Widget::InitParams GetWidgetParams() override;
+  bool UseCustomFrame() const override;
   bool UsesNativeSystemMenu() const override;
   int GetMinimizeButtonOffset() const override;
   bool ShouldSaveWindowPlacement() const override;
   void GetWindowPlacement(gfx::Rect* bounds,
                           ui::WindowShowState* show_state) const override;
 
   ~BrowserFrameAsh() override;
 
  private:
   class WindowPropertyWatcher;
 
   // Set the window into the auto managed mode.
   void SetWindowAutoManaged();
 
   // The BrowserView is our ClientView. This is a pointer to it.
   BrowserView* browser_view_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserFrameAsh);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_FRAME_BROWSER_FRAME_ASH_H_