[MD] Don't use new OTR native-theming when using a custom browser theme.

chrome/browser/ui/views/theme_copying_widget.h

+// Copyright 2016 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_THEME_COPYING_WIDGET_H_
+#define CHROME_BROWSER_UI_VIEWS_THEME_COPYING_WIDGET_H_
+
+#include "ui/views/widget/widget.h"
+
+// This widget uses a reference widget to provide its NativeTheme.
+class ThemeCopyingWidget : public views::Widget {
+ public:
+  explicit ThemeCopyingWidget(views::Widget* role_model);
+  ~ThemeCopyingWidget() override;
+
+  // views::Widget
+  const ui::NativeTheme* GetNativeTheme() const override;
+
+ private:
+  // The widget we'll copy our theme from. It's assumed to outlive |this|.

[sky, 2016/01/28 00:58:17]

nit: I would move the lifetime comment to the class description and/or
constructor. It's easy to miss it here.

[Evan Stade, 2016/01/28 01:47:05]

Done.

+  views::Widget* role_model_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThemeCopyingWidget);
+};
+
+#endif  // CHROME_BROWSER_UI_VIEWS_THEME_COPYING_WIDGET_H_