This is a quick Skia transcription of the Chromium tool at
src/skia/tools/filter_fuzz_stub.cc
to read and decode filters captured as .fil files.
R=joshualitt@google.com,mtklein@google.com,reed@google.com,robertphillips@google.com
BUG=487213
Review URL: https://codereview.chromium.org/1126423005