Add test for TextEditCommandAuraLinux::GetCommandString.

ui/base/ime/linux/text_edit_command_auralinux.cc

 // Copyright 2014 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 "ui/base/ime/linux/text_edit_command_auralinux.h"
 
 #include "base/logging.h"
 #include "ui/base/ime/text_edit_commands.h"
 
 namespace ui {
@@ skipping 102 matching lines @@
       return "Paste";
     case TextEditCommand::SELECT_ALL:
       return "SelectAll";
     case TextEditCommand::INSERT_TEXT:
       return "InsertText";
     case TextEditCommand::SET_MARK:
       return "SetMark";
     case TextEditCommand::UNSELECT:
       return "Unselect";
     case TextEditCommand::INVALID_COMMAND:
+    case TextEditCommand::NUMBER_OF_COMMANDS:
       NOTREACHED();
       return std::string();
   }
   NOTREACHED();
   return std::string();
 }
 
 }  // namespace ui