Add CSS property tracking to animations and transitions

This creates a histogram measuring how frequently each CSS property is
animated. Gathering this data will help us evaluate the impact of
accelerating/threading animations that are currently unaccelerated.

BUG=229405
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/19580004

git-svn-id: svn://svn.chromium.org/blink/trunk@154916 bbb929c8-8fbe-4397-9dbb-9b2b20218538