Don't treat ViewHostMsg_UpdateRect as a backing store message.

It doesn't actually give a new backing store to the browser, so it shouldn't unblock the UI thread.

BUG=

Review URL: https://codereview.chromium.org/288463004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271223 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/render_message_filter.cc

@@ -434,8 +434,6 @@ bool RenderMessageFilter::OnMessageReceived(const IPC::Message& message) {
 #endif
     IPC_MESSAGE_HANDLER_GENERIC(ViewHostMsg_SwapCompositorFrame,
         render_widget_helper_->DidReceiveBackingStoreMsg(message))
-    IPC_MESSAGE_HANDLER_GENERIC(ViewHostMsg_UpdateRect,
-        render_widget_helper_->DidReceiveBackingStoreMsg(message))
     IPC_MESSAGE_HANDLER(DesktopNotificationHostMsg_CheckPermission,
                         OnCheckNotificationPermission)
     IPC_MESSAGE_HANDLER(ChildProcessHostMsg_SyncAllocateSharedMemory,