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

base/i18n/base_i18n_switches.cc

Index: base/i18n/base_i18n_switches.cc
diff --git a/base/i18n/base_i18n_switches.cc b/base/i18n/base_i18n_switches.cc
new file mode 100644
index 0000000000000000000000000000000000000000..44e8393baab0b90c6e8bc53180d21482d6f09d5e
--- /dev/null
+++ b/base/i18n/base_i18n_switches.cc
@@ -0,0 +1,16 @@
+// 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.
+
+#include "base/i18n/base_i18n_switches.h"
+
+namespace switches {
+
+// Force the UI to a specific direction. Valid values are "ltr" (left-to-right)
+// and "rtl" (right-to-left).
+const char kForceUIDirection[]              = "force-ui-direction";
+
+const char kForceUIDirectionLTR[]           = "ltr";
+const char kForceUIDirectionRTL[]           = "rtl";
+
+}  // namespace switches