Refactor SerializedImageFilter to avoid duplicate code

After this CL, we have 3.5 options for fuzzing ImageFilter
1. Create it from API calls and then draw it
   fuzz -t api -n ImageFilter -b [input]

2. Deserialize a fuzzed stream into an ImageFilter (this is
what Chromium's  filter_fuzz_stub does)
   fuzz -t filter_fuzz -b [input]

3. Create an ImageFilter from API calls, serialize it, apply
some mutations to the stream, deserialize it, then draw it.
   fuzz -t api -n SerializedImageFilter -b [input]

3.5 Create ImageFilters as part of our more general canvas
fuzzers.
   fuzz -t api -n RasterN32Canvas -b [input] (and others)

Previously, the SerializedImageFilter had its own, slightly
stale and prone to stack-overflow way of making an image filter.
This CL re-uses what we already do for Canvas fuzzing and removes
that dead code.

Additionally, there is a way to easily generate a corpus
for the filter_fuzz type, via SerializedImageFilter.

Bug: skia:
Change-Id: I31bb4ffce2abf1c1a6d0a7000e5aceb8d7b38b65
Reviewed-on: https://skia-review.googlesource.com/92142
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
4 files changed