Consolidate base:: imports. This merges the mrucache and numerics into one folder, to prevent having to make two identical versions of logging. BUG=angleproject:2044 Change-Id: Iba6dab05b21eb9ba0de44f27a90579c590a9a7fd Reviewed-on: https://chromium-review.googlesource.com/522870 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>