Move border-collapse to be generated in ComputedStyleBase

Move the inherited property caption-side and its enum, EBorderCollapse,
to be generated in ComputedStyleBase. Also removed the explicit value
setters for EBorderCollapse and the one callsite where this was used
(implicit int conversion is not allowed for enum classes anyway).

BUG=628043

Review-Url: https://codereview.chromium.org/2550343002
Cr-Commit-Position: refs/heads/master@{#436523}
4 files changed