Refactoring: Do not create unused InputType objects.

HTMLInputElement::updateType should not create an InputType object in a case
that it won't be used.

This CL revert r156902, and re-land r156622.

BUG=277843
TEST=none; no behavior changes.

Review URL: https://chromiumcodereview.appspot.com/23517005

git-svn-id: svn://svn.chromium.org/blink/trunk@157339 bbb929c8-8fbe-4397-9dbb-9b2b20218538