GitLab

Calling base::LinkNode::Insert{Before,After} is invalid if it's
already in a list and can easily lead to undefined behavior. This
extracts them into a non-templated base and adds CHECKs.

Bug: None
Change-Id: Ib00fcd9ba513181336c4b02e846fa935fe5f46cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2405709
Commit-Queue: Collin Baker <collinbaker@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809092}