Add DCHECK to ensure IndexedDBDispatcher doesn't get re-created.

This could happen if there are IDB objects that survive the call to
didStopWorkerRunLoop.

BUG=121734
TEST=


Review URL: http://codereview.chromium.org/9999035

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@131679 0039d316-1c4b-4281-b951-d872f2087c98
void IndexedDBDispatcher::RequestIDBFactoryGetDatabaseNames(
    WebIDBCallbacks* callbacks_ptr,
    const string16& origin,
    WebFrame* web_frame) {
  ResetCursorPrefetchCaches();
  scoped_ptr<WebIDBCallbacks> callbacks(callbacks_ptr);

  if (!CurrentWorkerId() &&
      !ChildThread::current()->IsWebFrameValid(web_frame))
    return;

  IndexedDBHostMsg_FactoryGetDatabaseNames_Params params;
  params.thread_id = CurrentWorkerId();
  params.response_id = pending_callbacks_.Add(callbacks.release());
  params.origin = origin;
  Send(new IndexedDBHostMsg_FactoryGetDatabaseNames(params));
}

void IndexedDBDispatcher::RequestIDBFactoryGetDatabaseNames(
    WebIDBCallbacks* callbacks_ptr,
    const string16& origin,
    WebFrame* web_frame) {
  ResetCursorPrefetchCaches();
  scoped_ptr<WebIDBCallbacks> callbacks(callbacks_ptr);

  if (!CurrentWorkerId() &&
      !ChildThread::current()->IsWebFrameValid(web_frame))
    return;

  IndexedDBHostMsg_FactoryGetDatabaseNames_Params params;
  params.thread_id = CurrentWorkerId();
  params.response_id = pending_callbacks_.Add(callbacks.release());
  params.origin = origin;
  Send(new IndexedDBHostMsg_FactoryGetDatabaseNames(params));
}
