Revert of Change ComputedStyle::setUnique to take bool parameter. (patchset #1 id:1 of https://codereview.chromium.org/2677843002/ )

Reason for revert:
After discussion, it makes more sense for setUnique to take no arguments.

Original issue's description:
> Change ComputedStyle::setUnique to take bool parameter.
>
> Currently setUnique() takes no arguments and sets the corresponding
> nonproperty flag to be true. However, this is different to the
> traditional setters of property fields, where they set the field to an
> argument value. Instead of handling setUnique as a special case in the
> generator, we change setUnique to a normal setter that takes a boolean
> parameter. This decision was discussed in crrev.com/2667543002.
>
> This is prework for generating 'unique'.
>
> BUG=628043
>
> Review-Url: https://codereview.chromium.org/2677843002
> Cr-Commit-Position: refs/heads/master@{#448774}
> Committed: https://chromium.googlesource.com/chromium/src/+/25b1de1a5da3dbe754e4461cdd5c7ca2b3502ab6

TBR=sashab@chromium.org,esprehn@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=628043

Review-Url: https://codereview.chromium.org/2689983002
Cr-Commit-Position: refs/heads/master@{#449918}
12 files changed