Switch to Skia's new representation of linear gamma

Bug: 77276533
Test: CtsGraphicsTestCases ImageDecoderTest#testColorSpace
      ag/5244477

Although the old one works for [0,1], Skia has switched to this new
representation because it has the following nice properties:
- it extends cleanly above 1
- it's unambiguously defined

Having ColorSpace out of sync results in mismatches between those
objects underlying SkColorSpace objects when they should be the same.

Change-Id: Ie5cf223d6053718aded12b66ea58a874ce888903