Don't layout when isSelfPaintingLayer() changes

I can't find any reason to do a layout when the self painting bit
changes. The code was added by hyatt a long time ago in
https://trac.webkit.org/changeset/43657 but the test he added still
passes without that code (as do the rest of the tests).

Lets just delete this layout code.

Review URL: https://codereview.chromium.org/275563002

git-svn-id: svn://svn.chromium.org/blink/trunk@173614 bbb929c8-8fbe-4397-9dbb-9b2b20218538