GitLab

Step 1 of dropping HintCacheStore interface - it uses a using
definition to avoid more changes for this CL and keep diffs meaningful.
Next step will be to rename HintCacheLevelDBStore to HintCacheStore.

Change-Id: I94997cd0506ee834958f6096179128041d66557b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1539006Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Doug Arnett <dougarnett@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644906}