MacViews: Don't draw custom frame on Mac

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

 // 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.
 
 #include "chrome/browser/ui/views/frame/browser_frame_mac.h"
 
 #include "chrome/browser/ui/views/frame/browser_frame.h"
 
 BrowserFrameMac::BrowserFrameMac(BrowserFrame* browser_frame,
                                  BrowserView* browser_view)
     : views::NativeWidgetMac(browser_frame) {
 }
 
 BrowserFrameMac::~BrowserFrameMac() {
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // BrowserFrameMac, NativeBrowserFrame implementation:
 
 views::Widget::InitParams BrowserFrameMac::GetWidgetParams() {
   views::Widget::InitParams params;
   params.native_widget = this;
   return params;
 }
 
+bool BrowserFrameMac::UseCustomFrame() const {
+  return false;
+}
+
 bool BrowserFrameMac::UsesNativeSystemMenu() const {
   return true;
 }
 
 bool BrowserFrameMac::ShouldSaveWindowPlacement() const {
   return true;
 }
 
 void BrowserFrameMac::GetWindowPlacement(
     gfx::Rect* bounds,
     ui::WindowShowState* show_state) const {
   return NativeWidgetMac::GetWindowPlacement(bounds, show_state);
 }
 
 int BrowserFrameMac::GetMinimizeButtonOffset() const {
   NOTIMPLEMENTED();
   return 0;
 }