Deflake two animations tests.

-transitions/cancel-transition.html
Force layouts so that the setTimeouts are more likely to fire
at the right time with respect to the animation.

-transitions/suspend-transform-transition.html
Get rid of the extraneous setTimeout and shorten the timer so
that it's more likely the animation will pause in the "safe zone".
Hard to be sure if this will 100% get rid of the flake, but it works
for me locally.

BUG=303326

Review URL: https://codereview.chromium.org/25492007

git-svn-id: svn://svn.chromium.org/blink/trunk@158776 bbb929c8-8fbe-4397-9dbb-9b2b20218538