Revert "Never share pixels when we make a subset image"

This reverts commit 3eff2459d4a19462a8f24fb0a39a1d11a2487b9c.

Reason for revert: did I break abandongpu bot?

Original change's description:
> Never share pixels when we make a subset image
> 
> - mostly just affects Lazy images (raster was already always copying)
> - issue with other factories that offer subsetting
>    - (e.g. MakeFromGenerator)
>    - can we remove those options, and require makeSubset() afterwards?
> - greatly simplifies dealing with mipmaps
> 
> Landing this would obsolete
> https://skia-review.googlesource.com/c/skia/+/305960
> 
> Related: https://skia-review.googlesource.com/c/skia/+/306136
> 
> Related: https://bugs.chromium.org/p/skia/issues/detail?id=10544
> 
> Change-Id: I074420543bd2fcd46ed1620bbf0eed00371ab018
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/305970
> Commit-Queue: Mike Reed <reed@google.com>
> Reviewed-by: Leon Scroggins <scroggo@google.com>

TBR=mtklein@google.com,bsalomon@google.com,robertphillips@google.com,scroggo@google.com,brianosman@google.com,reed@google.com

Change-Id: Iab2f92855fe61e48f0e432b7257eb7ddef78fcfa
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/306377
Reviewed-by: Mike Reed <reed@google.com>
8 files changed