Revert 174521 "Change default force composite setting to true"

This change had the unexpected side-effect of causing some
browser_tests to fail or time out on the Chrome OS configuration.
Reverting in order to get Blink rolls going again.

BUG=361729,376531

> Change default force composite setting to true
> 
> BUG=361729
> 
> Review URL: https://codereview.chromium.org/261143003

TBR=enne@chromium.org

Review URL: https://codereview.chromium.org/298883008

git-svn-id: svn://svn.chromium.org/blink/trunk@174604 bbb929c8-8fbe-4397-9dbb-9b2b20218538