Split ColumnRule field in ComputedStyle.

Currently, column-rule related properties are being stored as a single
BorderValue called ColumnRule. However, it is possible to split
ColumnRule into its constituent fields and generate each of them
individually.

There should be no performance impact from this patch.

Diff: https://gist.github.com/955fa418e240be79c0521d7d53e26ca7/revisions

Bug: 628043
Change-Id: I31db806f2fc427eb996ba78ef56dce17e5bc83d5
Reviewed-on: https://chromium-review.googlesource.com/544479
Reviewed-by: nainar <nainar@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#481717}
5 files changed