[skottie] More robust font style parsing

  - both weight and slant are optional
  - handle arbitrary whitespace separators
  - case insensitive keys

Change-Id: Iadd3a43167cd71654d7578549bd331fde243c28f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/335822
Commit-Queue: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
2 files changed