[canvaskit] Remove exposition of SkData

Change-Id: I5a7c2e30b2adc4b8947743ac82a800e96a7005b1
Bug: skia:10717
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/370879
Reviewed-by: Nathaniel Nifong <nifong@google.com>
9 files changed