Revert "Preserve colorType and alphaType in SkImage::makeColorSpace"

This reverts commit d842557c07246546ff15aede9d3b4e078c62b7e4.

Reason for revert: Chrome roll failing CanvasAsyncBlobCreatorTest.ColorManagedConvertToBlob test.

Original change's description:
> 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>

TBR=mtklein@google.com,brianosman@google.com

Change-Id: I366b097644ac1fa920fc9addcad3e09c2a0a63cc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:8382
Reviewed-on: https://skia-review.googlesource.com/156184
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
11 files changed