Fix another race condition on worker process shutdown that results in use-aft...

chrome/renderer/webworker_proxy.cc

Index: chrome/renderer/webworker_proxy.cc
===================================================================
--- chrome/renderer/webworker_proxy.cc	(revision 28613)
+++ chrome/renderer/webworker_proxy.cc	(working copy)
@@ -97,6 +97,9 @@
   delete this;
 }
 
+void WebWorkerProxy::clientDestroyed() {
+}
+
 bool WebWorkerProxy::Send(IPC::Message* message) {
   // It's possible that postMessage is called before the worker is created, in
   // which case route_id_ will be none.  Or the worker object can be interacted