GitLab

Update BlinkGCDesign documentation

Remove outdated parts related to threads and safe points.

Change-Id: I1faa4368e0534440e87de7c2cf0fe2d30b9ad917
Reviewed-on: https://chromium-review.googlesource.com/1181013
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584687}