[graphite] Add ManagedGraphiteTexture.

This provides a wrapper around BackendTexture for auto-releasing,
similar to ManagedBackendTexture. Currently it only supports creation
via Pixmaps for simplicity.

Bug: b/274151809
Change-Id: I0a31d643e8de116e069fc31fa5f58145a46100b5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/657280
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
2 files changed