Bug 860490 - Mark _pluginthreadasynccall calls as safe to re-enter gecko. r=bsmedberg,roc

dom/plugins/base/nsNPAPIPlugin.cpp

@@ -776,7 +776,7 @@ nsPluginThreadRunnable::Run()
     PluginDestructionGuard guard(mInstance);
 
     NS_TRY_SAFE_CALL_VOID(mFunc(mUserData), nullptr,
-                          NS_PLUGIN_CALL_UNSAFE_TO_REENTER_GECKO);
+                          NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
   }
 
   return NS_OK;