Add chrome://flags entry for V8 Orinoco garbage collector

- Adds chrome://flags entry
- Adds a FeatureFlag
- Make the V8 --single-threaded-gc dependent on the Chrome flag

Bug: chromium:848670
Change-Id: I08c297867ad3e4ab3b3388525b129da497b1115c
Reviewed-on: https://chromium-review.googlesource.com/1082292
Reviewed-by: Mark Pearson <[email protected]>
Reviewed-by: Ulan Degenbaev <[email protected]>
Reviewed-by: Jochen Eisinger <[email protected]>
Reviewed-by: Kentaro Hara <[email protected]>
Commit-Queue: Hannes Payer <[email protected]>
Cr-Commit-Position: refs/heads/master@{#564395}
7 files changed