Add ScopedMacRTL class for Cocoa browser RTL testing

ui/base/cocoa/rtl_feature.mm

+// 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.
+
+#import "ui/base/cocoa/rtl_feature.h"
+
+#import <Cocoa/Cocoa.h>
+
+#include "base/i18n/rtl.h"
+#include "base/mac/mac_util.h"
+
+namespace ui {

[Robert Sesek, 2016/12/07 19:21:01]

nit: blank line after

[lgrey, 2016/12/07 19:34:21]

Done.

+const base::Feature kExperimentalMacRTL{"ExperimentalMacRTL",
+                                        base::FEATURE_DISABLED_BY_DEFAULT};
+
+bool ShouldDoExperimentalRTLLayout() {
+  return base::i18n::IsRTL() &&
+         base::FeatureList::IsEnabled(kExperimentalMacRTL);
+}
+
+bool ShouldFlipWindowControlsInRTL() {
+  return ShouldDoExperimentalRTLLayout() && base::mac::IsAtLeastOS10_12();
+}
+
+}  // namespace ui