Introduce a more generic version of IdType for opaque aliases

This one works with strings and other complex types in addition to
integrals.

Bug: 954080
Change-Id: Ic9961e0ccffdce89d160a5b4d8cab9b7d94a100b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617481
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Ɓukasz Anforowicz <lukasza@chromium.org>
Commit-Queue: Maciej Pawlowski <mpawlowski@opera.com>
Cr-Commit-Position: refs/heads/master@{#662532}
6 files changed