Add WebAssembly code gc field trial testing config

The feature was added in https://crrev.com/c/1578540. It's currently
finched in Canary and Dev and will soon be finched in beta (M-76).

R=jwd@chromium.org

Bug: 956480
Change-Id: I038e868fe5c43f3f8d214e62f6570ac1ef85d429
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628615
Auto-Submit: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663264}
1 file changed