Change Document::detach() to RELEASE_ASSERT all subframes are gone.

BUG=556724,577105

Review URL: https://codereview.chromium.org/1667573002

Cr-Commit-Position: refs/heads/master@{#373642}
void Document::removeAllEventListeners()
{
    ContainerNode::removeAllEventListeners();

    if (LocalDOMWindow* domWindow = this->domWindow())
        domWindow->removeAllEventListeners();
}

void Document::removeAllEventListeners()
{
    ContainerNode::removeAllEventListeners();

    if (LocalDOMWindow* domWindow = this->domWindow())
        domWindow->removeAllEventListeners();
}
