Add ScopedMacRTL class for Cocoa browser RTL testing

ui/base/test/scoped_mac_rtl.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 UI_BASE_TEST_SCOPED_MAC_RTL_H_

[tapted, 2016/12/07 23:20:27]

Why src/ui/base ? (Is there a plan to use this outside of src/chrome? or even
src/chrome/browser/ui?)

If not, I think this belongs somewhere under src/chrome -- perhaps
src/chrome/test/base or src/chrome/browser/ui/test 

(e.g. I think iOS uses stuff from here ui/base, which we sometimes need to tread
carefully around)

+#define UI_BASE_TEST_SCOPED_MAC_RTL_H_
+
+#include <string>
+
+#include "base/test/scoped_feature_list.h"
+
+namespace ui {
+
+// Enables all flags required for
+// |ui::ShouldDoExperimentalRTLLayout| to return true.
+class ScopedEnableMacRTLLayout final {

[tapted, 2016/12/07 23:20:27]

Since there's only one class in the file, it would be nice to have it match the
filename. Perhaps

scoped_force_rtl_mac.h/mm
ScopedForceRTLMac

(ending the file in _mac also means it's affected by the automatic platform
globbing more obviously that just having the .mm suffix - e.g. the .h won't be
checked for changes on non-mac platforms [i think])

+ public:
+  ScopedEnableMacRTLLayout();
+  ~ScopedEnableMacRTLLayout();
+
+ private:
+  BOOL original_apple_text_direction_;
+  BOOL original_rtl_writing_direction_;
+  std::string original_locale_;
+  base::test::ScopedFeatureList scoped_feature_list_;
+  DISALLOW_COPY_AND_ASSIGN(ScopedEnableMacRTLLayout);

[tapted, 2016/12/07 23:20:27]

nit: blank line before

+};
+
+}  // namespace ui
+
+#endif  // UI_BASE_TEST_SCOPED_MAC_RTL_H_