This takes the "one pass" code path more often, using less memory, as it
does not have to allocate an intermediate width*height pixel buffer.
Wuffs v0.2 did not support SRC_OVER, only SRC, but Wuffs v0.3 does.
The gif-transparent-index.gif test file comes from the
test/data/artificial directory of the github.com/google/wuffs
repository. It was programmatically generated.
The new GifTest.cpp test passes with skia_use_wuffs true or false, with
or without the SkWuffsCodec.cpp change.
Change-Id: I46fb4c849319fbefc39f331416a8b7d3836093ce
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/320116
Commit-Queue: Leon Scroggins <scroggo@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
