Decode to sRGB on Android

I want to land this so we can start testing color space aware
decoding on Android.  In particular, it will be interesting to
see how linear premultiplication will affect existing content.

This will only modify BitmapRegionDecoder behavior.  I'll
follow up with a similar change to BitmapFactory.cpp in Android.

This will cause image diffs on Gold.

BUG=skia:

Change-Id: Iffda5f035447f2608ce26945570b503f8971b735
Reviewed-on: https://skia-review.googlesource.com/5698
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
4 files changed