Disable frame navigations during DocumentLoader detach in FrameLoader::startLoad

BUG=613266

Review-Url: https://codereview.chromium.org/2006033002
Cr-Commit-Position: refs/heads/master@{#396241}
Node::InsertionNotificationRequest HTMLAnchorElement::insertedInto(ContainerNode* insertionPoint)
{
    InsertionNotificationRequest request = HTMLElement::insertedInto(insertionPoint);
    logAddElementIfIsolatedWorldAndInDocument("a", hrefAttr);
    return request;
}

Node::InsertionNotificationRequest HTMLAnchorElement::insertedInto(ContainerNode* insertionPoint)
{
    InsertionNotificationRequest request = HTMLElement::insertedInto(insertionPoint);
    logAddElementIfIsolatedWorldAndInDocument("a", hrefAttr);
    return request;
}
