A prior refactor had broken the method we used to cause test steps to
fail on API errors. This CL restores the path. We detected this when
analyzing a particular GLES trace that contained invalid GLES calls.

Bug: angleproject:5788
Change-Id: I26940e49cf73ce6050ea6ee274d5c5748835a167
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2782008
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>