PPAPI: Make CompletionCallbacks work right on background threads.

ppapi/tests/test_utils.h

Index: ppapi/tests/test_utils.h
diff --git a/ppapi/tests/test_utils.h b/ppapi/tests/test_utils.h
index ab87dd3e47bff4076099a96b924d058247fb788b..60f7fc444dbaef349fe0ab978f7210863545a76b 100644
--- a/ppapi/tests/test_utils.h
+++ b/ppapi/tests/test_utils.h
@@ -11,6 +11,7 @@
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/cpp/completion_callback.h"
+#include "ppapi/cpp/dev/message_loop_dev.h"
 #include "ppapi/utility/completion_callback_factory.h"
 
 // Timeout to wait for some action to complete.
@@ -152,6 +153,8 @@ class TestCompletionCallback {
 
  private:
   static void Handler(void* user_data, int32_t result);
+  void RunMessageLoop();
+  void QuitMessageLoop();
 
   // Used to check that WaitForResult is only called once for each usage of the
   // callback.
@@ -166,6 +169,7 @@ class TestCompletionCallback {
   unsigned run_count_;
   PP_Instance instance_;
   Delegate* delegate_;
+  pp::MessageLoop_Dev target_loop_;
 };
 
 // Verifies that the callback didn't record any errors. If the callback is run