Add new Codec fuzzers to FuzzMain

Already in oss-fuzz:
https://github.com/google/oss-fuzz/pull/1882

This tweaks some names and return types to be more
consistent.

Bug: skia:
Change-Id: Id7e2e00bd4e7c7758d616d102195c0291bc37d9f
Reviewed-on: https://skia-review.googlesource.com/c/163124
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
4 files changed