This will give the browsers the ability to control the cache size,
query and populate the contents, and trim cache contents on memory
pressure.

BUG=angleproject:1897

Change-Id: I6edaa7d307b890223db98792d5b074e4a7fdfaa4
Reviewed-on: https://chromium-review.googlesource.com/563606
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>