IndexedDB: Convert key types to mojom enum

Bug: 717812
Change-Id: Iaef4a1c54a0bbc5247df668f5ab5f33d5c7d5e1b
Reviewed-on: https://chromium-review.googlesource.com/c/1352622
Commit-Queue: Chase Phillips <cmp@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613613}
26 files changed