Add some additional safety net to the CSA code for triggering promise
reactions to make sure we catch security bugs (specifically related
to misuse of the V8 Extras API) on the fast-path.

Bug: chromium:931640, chromium:931949
Change-Id: I76b5dc6653e2404411a29dcd9c54245d7c43d883
Reviewed-on: https://chromium-review.googlesource.com/c/1485972Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59829}