GitLab

Adds two metrics logged every 5 minutes:
* Per-thumbnail compressed data memory usage
* Total compressed data memory usage

The former has a sample for each thumbnail every 5 minutes, while the
latter has exactly one every 5 minutes.

Bug: 11261624
Change-Id: I1595c6a6b771f73e3be9a5497d1cf6f6ec3d1af7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462685Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Dana Fried <dfried@chromium.org>
Commit-Queue: Collin Baker <collinbaker@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815714}