We also catch any errors that happen during running the
test or flushing. This allows them to show up in the CI logs.
For skottie-frames in particular, we stop clearing the canvas
before each render, as that was masking an error (and not how
we do things on skottie.skia.org).
Change-Id: I83936a35b6c314da76a0a64e15deaabd156e71f2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/421923
Reviewed-by: Kevin Lubick <kjlubick@google.com>
