Add HTMLFormControlElement::supportsAutofocus to fix a FIXME comment.

This virtual function should return true if the form control can hanlde
'autofocucs' attribute if it is specified.

Note: HTMLInputElement::supportsAutofocus reuses InputType::isInteractiveContent
because interactiveness is required for autofocus capability.

BUG=none
TEST=none; no behavior changes.

Review URL: https://codereview.chromium.org/143343003

git-svn-id: svn://svn.chromium.org/blink/trunk@165432 bbb929c8-8fbe-4397-9dbb-9b2b20218538
void HTMLTextAreaElement::defaultEventHandler(Event* event)
{
    if (renderer() && (event->isMouseEvent() || event->isDragEvent() || event->hasInterface(EventNames::WheelEvent) || event->type() == EventTypeNames::blur))
        forwardEvent(event);
    else if (renderer() && event->isBeforeTextInsertedEvent())
        handleBeforeTextInsertedEvent(static_cast<BeforeTextInsertedEvent*>(event));

    HTMLTextFormControlElement::defaultEventHandler(event);
}

void HTMLTextAreaElement::defaultEventHandler(Event* event)
{
    if (renderer() && (event->isMouseEvent() || event->isDragEvent() || event->hasInterface(EventNames::WheelEvent) || event->type() == EventTypeNames::blur))
        forwardEvent(event);
    else if (renderer() && event->isBeforeTextInsertedEvent())
        handleBeforeTextInsertedEvent(static_cast<BeforeTextInsertedEvent*>(event));

    HTMLTextFormControlElement::defaultEventHandler(event);
}
