Remove calls to deprecated MessageLoop methods in ppapi.

ppapi/proxy/tracked_callback_unittest.cc

Index: ppapi/proxy/tracked_callback_unittest.cc
diff --git a/ppapi/proxy/tracked_callback_unittest.cc b/ppapi/proxy/tracked_callback_unittest.cc
index 52a7723f4c3bb88849873737a39ee29519ac5446..30868013105842eed61b86b56dd9acbc5845a138 100644
--- a/ppapi/proxy/tracked_callback_unittest.cc
+++ b/ppapi/proxy/tracked_callback_unittest.cc
@@ -62,7 +62,7 @@ class CallbackThread : public base::SimpleThread {
     scoped_refptr<MessageLoopResource> message_loop(message_loop_);
     message_loop->AttachToCurrentThread();
     // Note, run releases the lock to run events.
-    message_loop->Run();
+    base::RunLoop().Run();
     message_loop->DetachFromThread();
   }