Reland "[skottie] Add drop shadow support"

This reverts commit 0b36acdad970ff3581a46bc114939637a5baa11c.

Reason for revert: Cannot repro build failure - maybe flake?  Trying again.

Original change's description:
> Revert "[skottie] Add drop shadow support"
> 
> This reverts commit 1f43a4359d7d1b2e6cae144c3f510c0ffa8e60ec.
> 
> Reason for revert: Android build failures.
> 
> Original change's description:
> > [skottie] Add drop shadow support
> > 
> > Introduce the machinery required for general image filters in SkSG +
> > a concrete drop shadow image filter effect.
> > 
> > Wire it all up with Skottie to support drop-shadow layer effects.
> > 
> > Change-Id: I98e9669852f58ba6481439a7fda4a56ec6c59b8a
> > Reviewed-on: https://skia-review.googlesource.com/c/190426
> > Reviewed-by: Mike Reed <reed@google.com>
> > Commit-Queue: Florin Malita <fmalita@chromium.org>
> 
> TBR=fmalita@chromium.org,reed@google.com
> 
> Change-Id: I31d38ed4d4a15b77d1d1218b2677a891978332cb
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://skia-review.googlesource.com/c/190981
> Reviewed-by: Florin Malita <fmalita@chromium.org>
> Commit-Queue: Florin Malita <fmalita@chromium.org>

TBR=fmalita@chromium.org,reed@google.com

Change-Id: Ic3f949f40ed4651715b6de906882f5f4522f91b9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/191040
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
9 files changed