[graphite] Add basic logging.

Just a placeholder for now until we have a better sense of what we want.

Bug: skia:12817
Change-Id: I75a76cb990c5a63bd2eefb5916ead3bff6742739
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/494036
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
9 files changed