Cancel JavaScript dialogs when an interstitial appears.

BUG=295695
TEST=See bug for repro steps.

Review URL: https://chromiumcodereview.appspot.com/24360011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225026 0039d316-1c4b-4281-b951-d872f2087c98
void WebContentsImpl::OnUserGesture() {
  FOR_EACH_OBSERVER(WebContentsObserver, observers_, DidGetUserGesture());

  ResourceDispatcherHostImpl* rdh = ResourceDispatcherHostImpl::Get();
  if (rdh)  // NULL in unittests.
    rdh->OnUserGesture(this);
}

void WebContentsImpl::OnUserGesture() {
  FOR_EACH_OBSERVER(WebContentsObserver, observers_, DidGetUserGesture());

  ResourceDispatcherHostImpl* rdh = ResourceDispatcherHostImpl::Get();
  if (rdh)  // NULL in unittests.
    rdh->OnUserGesture(this);
}
