PPAPI: Make PPB_MessageLoop_Dev::GetForMainThread work

ppapi/api/dev/ppb_message_loop_dev.idl

 /* Copyright (c) 2012 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.
  */
 
 /**
  * Defines the PPB_MessageLoop_Dev interface.
  */
 label Chrome {
   M18 = 0.1
@@ skipping 88 matching lines @@
  *
  *  - You quit the message loop via PostQuit with should_destroy set to
  *    PP_FALSE. In this case, the system will assume the message loop will be
  *    run again later and keep your tasks.
  *
  * To do proper shutdown, call PostQuit with should_destroy = PP_TRUE. This
  * will prohibit future work from being posted, and will allow the message loop
  * to run until all pending tasks are run.
  *
  * If you post a callback to a message loop that's been destroyed, or to an
- * invalid message loop, PostTask will return an error and will not run the
+ * invalid message loop, PostWork will return an error and will not run the
  * callback. This is true even for callbacks with the "required" flag set,
  * since the system may not even know what thread to issue the error callback
  * on.
  *
  * Therefore, you should check for errors from PostWork and destroy any
  * associated memory to avoid leaks. If you're using the C++
  * CompletionCallbackFactory, use the following pattern:
  *
  *   pp::CompletionCallback callback = factory_.NewOptionalCallback(...);
  *   int32_t result = message_loop.PostWork(callback);
@@ skipping 139 matching lines @@
    *
    * @return
    *   - PP_OK: The request to quit was successfully posted.
    *   - PP_ERROR_BADRESOURCE: The message loop was invalid.
    *   - PP_ERROR_WRONG_THREAD: You are attempting to quit the main thread.
    *     The main thread's message loop is managed by the system and can't be
    *     quit.
    */
   int32_t PostQuit([in] PP_Resource message_loop, PP_Bool should_destroy);
 };