Use invalidation sets for :invalid/:valid/:required/:optional.

Create invalidation sets for :invalid, :valid, :required, and :optional
pseudo classes and schedule invalidations instead of using
SubtreeStyleChange when those states change.

BUG=419873

Review URL: https://codereview.chromium.org/620333002

git-svn-id: svn://svn.chromium.org/blink/trunk@184392 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Get rid of synchronous accessibility notifications.

Blink is always in a separate process and messages are always
asynchronous, so there's no purpose in supporting synchronous
accessibility messages.

BUG=none

Review URL: https://codereview.chromium.org/666333003

git-svn-id: svn://svn.chromium.org/blink/trunk@184393 bbb929c8-8fbe-4397-9dbb-9b2b20218538