Reland "Switch SkPaint's color to SkColor4f"

This reverts commit cacf496a9d61d37b2e0d4ab76fac24cae78b0367.

Reason for revert: Android tests have been updated.

Original change's description:
> Revert "Switch SkPaint's color to SkColor4f"
> 
> This reverts commit ee87c8629cba96c2426ebbc1905c241af52f9ef0.
> 
> Reason for revert: Android tests.
> 
> Original change's description:
> > Switch SkPaint's color to SkColor4f
> > 
> > Change-Id: Ic2b83a05739720013a7c30ec014df0747b3f99a5
> > Reviewed-on: https://skia-review.googlesource.com/149229
> > Commit-Queue: Brian Osman <brianosman@google.com>
> > Reviewed-by: Mike Klein <mtklein@google.com>
> 
> TBR=djsollen@google.com,mtklein@google.com,brianosman@google.com,reed@google.com
> 
> Change-Id: I85efd020598d70cbfb90c4f4af7d33482a3d7280
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://skia-review.googlesource.com/151544
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>

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

Change-Id: Ifb817ab496fef22a7b1306af82186c6badbfa992
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/151664
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
9 files changed