Preserve colorType and alphaType in SkImage::makeColorSpace

Raster images were always converting to N32, and GPU images were
always converting to premul. These were unexpected and inconsistent.

Bug: skia:8382
Change-Id: I78fe6cff1208eef077a71d08e676cf8f8d5fed9a
Reviewed-on: https://skia-review.googlesource.com/156142
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
11 files changed