extend imageshader updater to handle perspective

- have to commit to a perspective stage (used to only use affine)
- coordinate between updater and shader/stages

Benches:

verts 608  --> 270
atlas 17.9 --> 5.6

Change-Id: I1d1ce9eb27b49d2ddcc610f6ea5c4720901b9e1b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/261136
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Reed <reed@google.com>
2 files changed