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 HTMLInputElement::setSelectionRangeForBinding(int start, int end, const String& direction, ExceptionState& exceptionState)
{
    if (!m_inputType->supportsSelectionAPI()) {
        exceptionState.throwDOMException(InvalidStateError, "The input element's type ('" + m_inputType->formControlType() + "') does not support selection.");
        return;
    }
    HTMLTextFormControlElement::setSelectionRange(start, end, direction);
}

void HTMLInputElement::setSelectionRangeForBinding(int start, int end, const String& direction, ExceptionState& exceptionState)
{
    if (!m_inputType->supportsSelectionAPI()) {
        exceptionState.throwDOMException(InvalidStateError, "The input element's type ('" + m_inputType->formControlType() + "') does not support selection.");
        return;
    }
    HTMLTextFormControlElement::setSelectionRange(start, end, direction);
}
