Revert "Improve support for :read-only and :read-write pseudoclasses."

This reverts commit r167629 (f3f2415b3b74e995665bea03f4316e28424fceeb)
as it caused a secuirty regression.

BUG=353143
TBR=andersr@opera.com

Review URL: https://codereview.chromium.org/221683005

git-svn-id: svn://svn.chromium.org/blink/trunk@170627 bbb929c8-8fbe-4397-9dbb-9b2b20218538