If JavaScript shows a dialog, cause the page to lose fullscreen.

BUG=670135, 550017, 726761, 728276

Review-Url: https://codereview.chromium.org/2906133004
Cr-Commit-Position: refs/heads/master@{#478884}
void WebContentsImpl::FriendWrapper::AddCreatedCallbackForTesting(
    const CreatedCallback& callback) {
  g_created_callbacks.Get().push_back(callback);
}

void WebContentsImpl::FriendWrapper::AddCreatedCallbackForTesting(
    const CreatedCallback& callback) {
  g_created_callbacks.Get().push_back(callback);
}
