GitLab

Move roots marking into ThreadState as most necessary data structures
do not live in ThreadHeap but ThreadState.

Bug: chromium:843903
Change-Id: I5e4f56f594911ebc0d9a17dcdfb4834c6befa555
Reviewed-on: https://chromium-review.googlesource.com/1189864
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586272}