This fixes a bug with the following sequence:
Make SkSurface_Raster, draw to it
snap an image, A, from the surface
make image B by calling withDefaultMipmaps() on image A
Let image A be destroyed.
draw to surface again
snap another image, C, from the surface
Image C and image B would now share the same SkPixelRef, reflecting
the final contents of the SkSurface.
Add a GM that exercises the bug when run through either the pic- or
serialize- vias and DDL.
Bug: skia:13111
Change-Id: Ib079163c84f420baf62fa7960110386303b8fb93
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/525517
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
e4601b0864