Adding more logs to pin down RAF flakiness.

I am pretty sure the flakiness comes from compositor in chromium side,
but temporarily adding these logs to make sure.

Will remove once we figure out what's wrong.

BUG=393331
TEST=bots
R=kbr@chromium.org,jamesr@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/514993002

git-svn-id: svn://svn.chromium.org/blink/trunk@181052 bbb929c8-8fbe-4397-9dbb-9b2b20218538