GitLab

This lifts the base/task/intrusive_heap container to base/containers, and
makes it fully STL-like.

Change-Id: I511ca1e675d37b46ec4049663c564ce490706e54
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1739411
Commit-Queue: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Albert J. Wong <ajwong@chromium.org>
Reviewed-by: Alex Clarke <alexclarke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689656}