MenuButton: support Mac look & feel

ui/gfx/scoped_canvas.cc

+// 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.
+
+#include "ui/gfx/scoped_canvas.h"
+
+#include "base/i18n/rtl.h"
+
+namespace gfx {
+
+ScopedRTLFlipCanvas::ScopedRTLFlipCanvas(gfx::Canvas* canvas, gfx::Rect rect)
+    : canvas_(canvas) {
+  if (base::i18n::IsRTL()) {
+    canvas->Translate(gfx::Vector2d(rect.width(), 0));
+    canvas->Scale(-1, 1);
+  }
+}
+
+}  // namespace gfx