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
WebContents* WebContentsImpl::GetEmbedderWebContents() const {
  BrowserPluginGuest* guest = GetBrowserPluginGuest();
  if (guest)
    return guest->embedder_web_contents();
  return NULL;
}

WebContents* WebContentsImpl::GetEmbedderWebContents() const {
  BrowserPluginGuest* guest = GetBrowserPluginGuest();
  if (guest)
    return guest->embedder_web_contents();
  return NULL;
}
