GitLab

* Convert enum -> enum class
* Rename values for consistency and clarity
* Rename/modify helpers for brevity and clarity
* Move values and helpers to .cc to keep .h shorter
* Use helpers more consistently

Bug: none
Change-Id: I12987b7c7dd8dd4589bbada0f23688309ece95fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2256362
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781921}