Remove COMPOSITOR_FILTER_OUTSETS references.

Also clean up some conditionals and remove pointless assert.

R=senorblanco@chromium.org,vollick@chromium.org
BUG=352228

Review URL: https://codereview.chromium.org/196553005

git-svn-id: svn://svn.chromium.org/blink/trunk@169164 bbb929c8-8fbe-4397-9dbb-9b2b20218538