Tighten isAllowedToQueryCompositingState up to InCompositingUpdate

This CL tightens the isAllowedToQueryCompositingState to disallow querying
compositing information until we're actually performing a compositing
update.

R=ojan@chromium.org
BUG=282720

Review URL: https://codereview.chromium.org/161283002

git-svn-id: svn://svn.chromium.org/blink/trunk@167059 bbb929c8-8fbe-4397-9dbb-9b2b20218538