GitLab

- Migrate to range for loops in KeycodeConverter.
- Fix naming of DOM |key| and |code| mapping table constants.
- Replace NULL with nullptr.

Change-Id: I1d4ae6146afa9bb32083e40c474653a1f6d1ec57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2022666
Auto-Submit: Wez <wez@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735414}