The cache is initialized from the application's blob cache and is
occasionally written back to it for disk storage.

Bug: angleproject:2516
Change-Id: I4cba4b00a7b9641c2983ef07159bc62cd10a5519
Reviewed-on: https://chromium-review.googlesource.com/1241373Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@google.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>