Remove CachedFormat remnants

Portions of this API will be updated again to support decode-to-dst, but
I want to clean up the old API first. I left a bunch of TODO breadcrumbs
for that work.

Change-Id: I25a29ccc14aa568e5ea84747d74244874afab9d9
Reviewed-on: https://skia-review.googlesource.com/146380
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed