Transform improvements

 - special case x == 1 in approx_powf()
 - skip gamut transforms when src gamut == dst gamut
 - add test of sRGB byte to linear sRGB float

Change-Id: Ib7a41d80afa456fc69924efb4ca4e230e15a6a01
Reviewed-on: https://skia-review.googlesource.com/113718
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed