Move LengthSizes border-*-radius out of BorderData

In StyleSurroundData, the border longhand properties are stored in a
single BorderData. This makes it difficult to generate because the
generator assumes that properties don't share storage.

This patch splits the LenthSize objects maintaining the border-*-radius
into individual properties stored directly on the surround group
instead.

Generated files diff here: https://gist.github.com/nainar/3192118aab7de3831137a4ae2cc73958/revisions

BUG=628043

Review-Url: https://codereview.chromium.org/2850173003
Cr-Commit-Position: refs/heads/master@{#468907}
9 files changed