[graphite] Fix bugs in RasterPathAtlas caching.

* Ensure we clear the cached data when resetting a Page
* Set the offset in the data matching the dirtyRect
* Clear dirtyRect after an upload

Bug: b/291735945
Change-Id: I20dad35efa0dc48da78c3cc8a90ff564eef23699
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/765096
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Arman Uguray <armansito@google.com>
Reviewed-by: Nicolette Prevost <nicolettep@google.com>
1 file changed