Setting input.x-webkit-speech should not cause focus change

In r150866, we introduced element()->focus() in destroyShadowSubtree()
to retain focus on <input> when its type attribute gets changed.
But when x-webkit-speech attribute is changed, the element is detached
before calling destroyShadowSubtree() and element()->focus() failed
This patch moves detach() after destroyShadowSubtree() to fix the
problem.

BUG=243818
TEST=fast/forms/input-type-change-focusout.html
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/16084005

git-svn-id: svn://svn.chromium.org/blink/trunk@151444 bbb929c8-8fbe-4397-9dbb-9b2b20218538
bool HTMLInputElement::getAllowedValueStep(Decimal* step) const
{
    return m_inputType->getAllowedValueStep(step);
}

bool HTMLInputElement::getAllowedValueStep(Decimal* step) const
{
    return m_inputType->getAllowedValueStep(step);
}
