PPAPI: Make CompletionCallbacks work right on background threads.

webkit/plugins/ppapi/host_globals.cc

Index: webkit/plugins/ppapi/host_globals.cc
diff --git a/webkit/plugins/ppapi/host_globals.cc b/webkit/plugins/ppapi/host_globals.cc
index 643ea8c376087e54799f0ff9ee802596d4f15ee1..7ab611da67ec6bfef246aa27cc4a66cb8984d81e 100644
--- a/webkit/plugins/ppapi/host_globals.cc
+++ b/webkit/plugins/ppapi/host_globals.cc
@@ -178,6 +178,10 @@ void HostGlobals::BroadcastLogWithSource(PP_Module pp_module,
      (*i)->element().document().frame()->addMessageToConsole(message);
 }
 
+::ppapi::MessageLoopShared* HostGlobals::GetCurrentMessageLoop() {
+  return NULL;
+}
+
 PP_Module HostGlobals::AddModule(PluginModule* module) {
 #ifndef NDEBUG
   // Make sure we're not adding one more than once.