[graphite] Fix assert in Viewer when displaying anisomips GM.

The anisomips GM appears to snap an image from a surface and samples it.
Because we haven't implemented that yet, validation of that texture
fails, which in turns means we don't insert a Recording into the
Context, and hence that Context has no CommandBuffer.

Added a message when we fail to validate TextureInfo, and pushed the
CommandBuffer submit in GraphiteMetalWindowContext inside the block
that checks to see if we have a Recording.

Change-Id: I74d8886a56ff703f7550bde321a4c3efbac66f30
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/550708
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
3 files changed