Remove Attr.isId and Attr.ownerElement.

These properties were removed in DOM4
<http://dom.spec.whatwg.org/#interface-attr>. Use counters
AttributeIsId and AttributeOwnerElement indicate they're rarely used
on the web (<0.01%.)

BUG=305105

Review URL: https://codereview.chromium.org/124643003

git-svn-id: svn://svn.chromium.org/blink/trunk@164820 bbb929c8-8fbe-4397-9dbb-9b2b20218538