That saves some bytes on the frontend side and some cycles when generating and parsing protocol JSON for stacks.
BUG=chromium:946411

Change-Id: I36b3a48b5d8246a05b877bc21f36c08803a1c304
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1542800
Commit-Queue: Alexei Filippov <alph@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60532}