Add MacRTL feature to flags

chrome/browser/flag_descriptions.h

 // Copyright 2017 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 CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
 #define CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
 
 // Includes needed for macros allowing conditional compilation of some strings.
 #include "build/build_config.h"
 #include "build/buildflag.h"
@@ skipping 3417 matching lines @@
 // default search engine.
 extern const char kUseGoogleLocalNtpName[];
 extern const char kUseGoogleLocalNtpDescription[];
 
 // Name and description for the flag to show a OneGoogleBar on the local NTP.
 extern const char kOneGoogleBarOnLocalNtpName[];
 extern const char kOneGoogleBarOnLocalNtpDescription[];
 
 #endif
 
+#if defined(OS_MACOSX)
+
+// Name and description of the flag that enables RTL in
+// Cocoa browser.
+extern const char kMacRTLName[];
+extern const char kMacRTLDescription[];
+
+#endif  // defined(OS_MACOSX)
+
 }  // namespace flag_descriptions
 
 #endif  // CHROME_BROWSER_FLAG_DESCRIPTIONS_H_