Added --force-ui-direction flag for developers to force LTR or RTL.

base/i18n/base_i18n_switches.h

Index: base/i18n/base_i18n_switches.h
diff --git a/base/i18n/base_i18n_switches.h b/base/i18n/base_i18n_switches.h
new file mode 100644
index 0000000000000000000000000000000000000000..f00cff34acb44dc06d6f747f947774cdca8b05d9
--- /dev/null
+++ b/base/i18n/base_i18n_switches.h
@@ -0,0 +1,20 @@
+// Copyright 2015 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 BASE_I18N_BASE_I18N_SWITCHES_H_
+#define BASE_I18N_BASE_I18N_SWITCHES_H_
+
+#include "base/i18n/base_i18n_export.h"
+
+namespace switches {
+
+BASE_I18N_EXPORT extern const char kForceUIDirection[];
+
+// kForceUIDirection choices.
+BASE_I18N_EXPORT extern const char kForceUIDirectionLTR[];
+BASE_I18N_EXPORT extern const char kForceUIDirectionRTL[];
+
+}  // namespace switches
+
+#endif  // BASE_I18N_BASE_I18N_SWITCHES_H_