Make Platform errors trigger test failures. This can be useful in the Vulkan back-end to make validation layer errors cause test cases to fail. BUG=angleproject:1319 Change-Id: I523f3c874e892a2646600e4c5c554319ed8d770c Reviewed-on: https://chromium-review.googlesource.com/342050 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>