Add SkSourceGammaTreatment enum so we know how to create mips

src/effects/gradients/SkRadialGradient.cpp

Index: src/effects/gradients/SkRadialGradient.cpp
diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index abd1f9e6cf2ab27526e32be969bf51280d11d010..a0fee273d7b4e02546044a1c179dee671d1c7806 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -313,7 +313,8 @@ const GrFragmentProcessor* GrRadialGradient::TestCreate(GrProcessorTestData* d)
     int colorCount = RandomGradientParams(d->fRandom, colors, &stops, &tm);
     auto shader = SkGradientShader::MakeRadial(center, radius, colors, stops, colorCount, tm);
     const GrFragmentProcessor* fp = shader->asFragmentProcessor(d->fContext,
-        GrTest::TestMatrix(d->fRandom), NULL, kNone_SkFilterQuality);
+        GrTest::TestMatrix(d->fRandom), NULL, kNone_SkFilterQuality,
+        SkSourceGammaTreatment::kRespect);
     GrAlwaysAssert(fp);
     return fp;
 }
@@ -341,7 +342,8 @@ const GrFragmentProcessor* SkRadialGradient::asFragmentProcessor(
                                                  GrContext* context,
                                                  const SkMatrix& viewM,
                                                  const SkMatrix* localMatrix,
-                                                 SkFilterQuality) const {
+                                                 SkFilterQuality,
+                                                 SkSourceGammaTreatment) const {
     SkASSERT(context);
 
     SkMatrix matrix;