Fix for 37477. r=pavlov,av. a=av.

layout/base/src/nsPluginViewer.cpp

@@ -796,7 +796,7 @@ NS_IMETHODIMP pluginInstanceOwner :: CreateWidget(void)
     }
     else if (nsnull != mWindow)
     {
-      mPluginWindow.window = (nsPluginPort *)mWindow->GetNativeData(NS_NATIVE_WINDOW);
+      mPluginWindow.window = (nsPluginPort *)mWindow->GetNativeData(NS_NATIVE_PLUGIN_PORT);
       mPluginWindow.type = nsPluginWindowType_Window;
     }
     else