experimental/minimal_ios_mtl_skia_app: clean up

Motivation: make is easier to add multiple views sharing a GrContext.

  - Split configure_mtk_view() from to_context()
  - AppViewDelegate no longer owns GrContext
  - Split out config_paint() and draw_example() fns
    to delineate example code from useful code.
  - AppViewDelegate no longer responsible for initializing
  - AppViewController owns MTLDevice and GrContext.

No-Try: true
Change-Id: I608da76c7818b262c0bfbe52dd431f3007e86e2d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/240201
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
1 file changed