Send layer squashing back to test mode while we iron out more bugs.

BUG=370410
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/274763002

git-svn-id: svn://svn.chromium.org/blink/trunk@173568 bbb929c8-8fbe-4397-9dbb-9b2b20218538