Fix the comment of PPB_MessageLoop.PostWork()

ppapi/cpp/message_loop.h

Index: ppapi/cpp/message_loop.h
diff --git a/ppapi/cpp/message_loop.h b/ppapi/cpp/message_loop.h
index 1439f5fab946a41d9d34c04c372fed5b37c6a7a9..fa38c669ef66599dcba588ffca7dd75912f32f74 100644
--- a/ppapi/cpp/message_loop.h
+++ b/ppapi/cpp/message_loop.h
@@ -118,7 +118,7 @@ class InstanceHandle;
 ///
 ///   pp::CompletionCallback callback = factory_.NewOptionalCallback(...);
 ///   int32_t result = message_loop.PostWork(callback);
-///   if (result != PP_OK_COMPLETIONPENDING)
+///   if (result != PP_OK)
 ///     callback.Run(result);
 ///
 /// This will run the callback with an error value, and assumes that the
@@ -224,9 +224,9 @@ class MessageLoop : public Resource {
   /// PP_FALSE. It will be queued until the next invocation of Run().
   ///
   /// @return
-  ///   - PP_OK_COMPLETIONPENDING: The work was posted to the message loop's
-  ///     queue. As described above, this does not mean that the work has been
-  ///     or will be executed (if you never run the message loop after posting).
+  ///   - PP_OK: The work was posted to the message loop's queue. As described
+  ///     above, this does not mean that the work has been or will be executed
+  ///     (if you never run the message loop after posting).
   ///   - PP_ERROR_BADRESOURCE: The given message loop resource is invalid.
   ///   - PP_ERROR_BADARGUMENT: The function pointer for the completion callback
   ///     is null (this will be the case if you pass PP_BlockUntilComplete()).