When investigating issues with apps it's handy to see the actual enum
value, not just that it's an invalid value.

Based on http://crrev.com/c/2182578 by Courtney Goeltzenleuchter.

Bug: b/155487768
Change-Id: I91611cb620a3bf2d302d667e0f168ca5cb6c9d3c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2507637
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>