Renamed members of EPointerEvents to match CSSValueKeywords.in.

Renamed members of EPointerEvents to match the keywords to the
values in CSSValueKeywords.in. This is a rename only - there are
no logic changes.

This is pre-work to move EPointerEvents to be generated in
ComputedStyleBase.

BUG=628043

Review-Url: https://codereview.chromium.org/2554673002
Cr-Commit-Position: refs/heads/master@{#436503}
8 files changed