Change default force composite setting to true

BUG=361729

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=174521

Review URL: https://codereview.chromium.org/261143003

git-svn-id: svn://svn.chromium.org/blink/trunk@174734 bbb929c8-8fbe-4397-9dbb-9b2b20218538