Add support for calling functions within the interpreter

Change-Id: Id009aa32faa40e9847dcf3668f1fd15e8b95dc56
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/213134
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
6 files changed