Sheriff-O-Matic: Transition more unit tests to mocha.

I've switched from using requestAnimationFrame to setTimeout because:

1. requestAnimationFrame will cause timeouts if the tab is in the background while the tests are running
2. setTimeout is less verbose, since we can just pass the function name itself (requestAnimationFrame calls the function with a parameter, which would break the "done" function, so we have to wrap it in an anonymous function)

BUG=40038
R=ojan@chromium.org,esprehn@chromium.org

Review URL: https://codereview.chromium.org/462453002

git-svn-id: svn://svn.chromium.org/blink/trunk@179988 bbb929c8-8fbe-4397-9dbb-9b2b20218538