Revert "Make compositingState explicit (re-land #2 with bogus ASSERT removed)"

This is in an attempt to remove the crashing occurring on tip of tree.
There's no strong reason to suspect this patch except that this patch
was a bit large.

BUG=306096
TBR=kareng@chromium.org, vollick@chromium.org

Review URL: https://codereview.chromium.org/27030009

git-svn-id: svn://svn.chromium.org/blink/trunk@159473 bbb929c8-8fbe-4397-9dbb-9b2b20218538