MacViews: Don't draw custom frame on Mac

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

 // Copyright 2014 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_MAC_H_
 #define CHROME_BROWSER_UI_VIEWS_FRAME_BROWSER_FRAME_MAC_H_
 
 #include "chrome/browser/ui/views/frame/native_browser_frame.h"
 #include "ui/views/widget/native_widget_mac.h"
 
 class BrowserFrame;
 class BrowserView;
 
 ////////////////////////////////////////////////////////////////////////////////
 //  BrowserFrameMac is a NativeWidgetMac subclass that provides
 //  the window frame for the Chrome browser window.
 //
 class BrowserFrameMac : public views::NativeWidgetMac,
                         public NativeBrowserFrame {
  public:
   BrowserFrameMac(BrowserFrame* browser_frame, BrowserView* browser_view);
 
   // Overridden from NativeBrowserFrame:
   views::Widget::InitParams GetWidgetParams() override;
+  bool UseCustomFrame() const override;
   bool UsesNativeSystemMenu() const override;
   bool ShouldSaveWindowPlacement() const override;
   void GetWindowPlacement(gfx::Rect* bounds,
                           ui::WindowShowState* show_state) const override;
 
  protected:
   ~BrowserFrameMac() override;
 
   // Overridden from NativeBrowserFrame:
   int GetMinimizeButtonOffset() const override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BrowserFrameMac);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_FRAME_BROWSER_FRAME_MAC_H_