add new source list in prep for separating imagefilters from other effects

Future Skia CL: https://skia-review.googlesource.com/c/skia/+/135566
Chrome CL: https://chromium-review.googlesource.com/c/chromium/src/+/1105062

Bug: skia:
Change-Id: I0caee985deb38739267b18fd92f3d0cf9454b8cd
Reviewed-on: https://skia-review.googlesource.com/135622
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed