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
HTMLSelectElement::HTMLSelectElement(Document& document, HTMLFormElement* form, bool createdByParser)
    : HTMLFormControlElementWithState(selectTag, document, form)
    , m_typeAhead(this)
    , m_size(0)
    , m_lastOnChangeIndex(-1)
    , m_activeSelectionAnchorIndex(-1)
    , m_activeSelectionEndIndex(-1)
    , m_isProcessingUserDrivenChange(false)
    , m_multiple(false)
    , m_activeSelectionState(false)
    , m_shouldRecalcListItems(false)
    , m_isParsingInProgress(createdByParser)
{
    ScriptWrappable::init(this);
}

HTMLSelectElement::HTMLSelectElement(Document& document, HTMLFormElement* form, bool createdByParser)
    : HTMLFormControlElementWithState(selectTag, document, form)
    , m_typeAhead(this)
    , m_size(0)
    , m_lastOnChangeIndex(-1)
    , m_activeSelectionAnchorIndex(-1)
    , m_activeSelectionEndIndex(-1)
    , m_isProcessingUserDrivenChange(false)
    , m_multiple(false)
    , m_activeSelectionState(false)
    , m_shouldRecalcListItems(false)
    , m_isParsingInProgress(createdByParser)
{
    ScriptWrappable::init(this);
}
