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}
void HTMLAnchorElement::dispatchFocusEvent(Element* oldFocusedElement, WebFocusType type, InputDeviceCapabilities* sourceCapabilities)
{
    if (type != WebFocusTypePage)
        m_wasFocusedByMouse = type == WebFocusTypeMouse;
    HTMLElement::dispatchFocusEvent(oldFocusedElement, type, sourceCapabilities);
}

void HTMLAnchorElement::dispatchFocusEvent(Element* oldFocusedElement, WebFocusType type, InputDeviceCapabilities* sourceCapabilities)
{
    if (type != WebFocusTypePage)
        m_wasFocusedByMouse = type == WebFocusTypeMouse;
    HTMLElement::dispatchFocusEvent(oldFocusedElement, type, sourceCapabilities);
}
