Reland #2 "[DevTools] Prevent JSONReader::Read errors from invalid unicode points"

I identified another cause of flakiness in the test and fixed it. This
time I also ran repeatedly on windows for hours with network service
enabled to make sure it never fails.

Bug: 824174
Change-Id: Icbaf26a733c89c8a4cf79cad26ab1d2675da5c8a
Reviewed-on: https://chromium-review.googlesource.com/c/1413255
Reviewed-by: Dmitry Gozman <[email protected]>
Reviewed-by: Devlin <[email protected]>
Commit-Queue: Joey Arhar <[email protected]>
Cr-Commit-Position: refs/heads/master@{#623129}
5 files changed