Revert of Initial value for mask-repeat property should be no-repeat (patchset #2 id:20001 of https://codereview.chromium.org/2169343002/ )

Reason for revert:
This appears to be causing crbug.com/645000

Original issue's description:
> Initial value for mask-repeat property should be no-repeat
>
> Spec: https://www.w3.org/TR/css-masking-1/#the-mask-repeat
>
> BUG=628968
>
> Committed: https://crrev.com/b76fc4469acf4c44336dd8d42d1e127c8823d08b
> Cr-Commit-Position: refs/heads/master@{#407435}

TBR=timloh@chromium.org,ramya.v@samsung.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=628968

Review-Url: https://codereview.chromium.org/2332373003
Cr-Commit-Position: refs/heads/master@{#418411}
6 files changed