Remove WebFrame::canHaveSecureChild

To simplify the public API, ServiceWorkerNetworkProvider can do the
parent walk itself.

Follow-up to https://crrev.com/ad1850962644e19.

BUG=607543

Review-Url: https://codereview.chromium.org/2082493002
Cr-Commit-Position: refs/heads/master@{#400896}
void Document::removeFocusedElementOfSubtree(Node* node, bool amongChildrenOnly)
{
    if (!m_focusedElement)
        return;

    if (!node->inShadowIncludingDocument())
        return;
    bool contains = node->isShadowIncludingInclusiveAncestorOf(m_focusedElement.get());
    if (contains && (m_focusedElement != node || !amongChildrenOnly))
        clearFocusedElement();
}

void Document::removeFocusedElementOfSubtree(Node* node, bool amongChildrenOnly)
{
    if (!m_focusedElement)
        return;

    if (!node->inShadowIncludingDocument())
        return;
    bool contains = node->isShadowIncludingInclusiveAncestorOf(m_focusedElement.get());
    if (contains && (m_focusedElement != node || !amongChildrenOnly))
        clearFocusedElement();
}
