Revert "Remove legacy shader context support from SkPictureShader"

This reverts commit b50f741ef341f870ebf4edfc172879e92843b80b.

Reason for revert: Perf regressions on the tree, and in chromium

Original change's description:
> Remove legacy shader context support from SkPictureShader
>
> This really doesn't need the hyper-optimized blitting performance.
>
> Change-Id: I0ac6bacd9a56836bd85fde31eb73586319f0d372
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/603422
> Reviewed-by: Herb Derby <herb@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>

Bug: chromium:1383486
Change-Id: I64c08e1561189846004b50e66c0d1229bed2565c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/607057
Commit-Queue: Brian Osman <brianosman@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
2 files changed