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Address cache is only actively used during roots marking. For
incremental marking we pass over roots multiple times, each time
potentially requires clearing the cache.

Drive-by:
- Add unit tests
- Rename to AddressCache
- Encapsulate handling fully in AddressCache
- Remove outdated caller

Bug: chromium:757440, chromium:830196
Change-Id: I51780e0bbbb8566ad0c83df98229e15133b42825
Reviewed-on: https://chromium-review.googlesource.com/1044214
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Keishi Hattori <keishi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556439}