hide legacy scalePixels and makeShader

Change-Id: Idae1e44aa0417adb943fd20112fb4f1fa81167f2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/337719
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
14 files changed