Revert "added skeletal animation support to GPU backend"

This reverts commit d275ef501c8e6ea6444912e22c29e2d13a3dfb53.

Reason for revert: Failing to compile on debian9.

Original change's description:
> added skeletal animation support to GPU backend
> 
> Pulled from reverted CL: https://skia-review.googlesource.com/c/skia/+/138596
> 
> Bug: skia:
> Change-Id: Ie07f1c76bae65c219ebe93d071bb19f1a30100c2
> Reviewed-on: https://skia-review.googlesource.com/139282
> Reviewed-by: Brian Osman <brianosman@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Commit-Queue: Ruiqi Mao <ruiqimao@google.com>

TBR=robertphillips@google.com,brianosman@google.com,ruiqimao@google.com

Change-Id: Ibc0da6ce16f078ff74a2c1bcab30750baff460f7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/140381
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Joe Gregorio <jcgregorio@google.com>
9 files changed