Reduce recalc/layout during the compositing of animated values.

Previously we would cause a recalc and layout for each animated
target/property pair, for every frame. With this change only one recalc/layout
is required per frame.
Reformat test-calc-checks
Rebaseline test-calc-checks
Merge pull request #354 from dstockwell/reduce-recalc-layout

Reduce recalc/layout during the compositing of animated values.
Avoid generating calc() expressions when just adding a 0 value.
Merge pull request #357 from dstockwell/simple-calc

Avoid generating calc() expressions when just adding a 0 value.
Merge pull request #353 from mithro/master

Merging testharness_* files into bootstrap.js
Merge pull request #361 from mithro/master

Adding pause/go button.
Adding FireFox to the run, but don't make the build fail.