GitLab

Cleanup V8 histograms

- mark obsolete histograms as such
- update descriptions and owners for current histograms
- add missing histograms

BUG=none
R=asvitkine@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/563853003

Cr-Commit-Position: refs/heads/master@{#295054}