Revert of Exact Ganesh Gradients for Special Cases (patchset #9 id:160001 of https...

Revert of Exact Ganesh Gradients for Special Cases (patchset #9 id:160001 of https://codereview.chromium.org/2223203003/ )

Reason for revert:
specualtive revert to fix valgrind bot
Perf-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-Valgrind

Original issue's description:
> Remove generalized gradient code
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2223203003
>
> Committed: https://skia.googlesource.com/skia/+/0c63006b88a16e3418d92852a62771615799839d
> Committed: https://skia.googlesource.com/skia/+/99818d69372d29a139935cfe5c379e491432931b
> Committed: https://skia.googlesource.com/skia/+/2a4959181fc98d5d7ee862e7cd1c7993b3343be6

TBR=bsalomon@google.com,fmenozzi@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review-Url: https://codereview.chromium.org/2245533005