Removed unused fallback code

Change-Id: I2dc9cde4bd7b7b54e7de677455b38fb3c9b86edb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/198242
Auto-Submit: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>