Add compositing states to DocumentLifecycle state machine

This CL adds two compositing states to the DocumentLifecycle state machine.
This state machine will help us avoid introducing new chicken-and-egg
relationships between style, layout, and compositing state.

BUG=341627

Review URL: https://codereview.chromium.org/158553002

git-svn-id: svn://svn.chromium.org/blink/trunk@166792 bbb929c8-8fbe-4397-9dbb-9b2b20218538