Add SkSourceGammaTreatment enum so we know how to create mips

src/effects/gradients/SkGradientShader.cpp

Index: src/effects/gradients/SkGradientShader.cpp
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 3c4784702ab36cadf12544fd6fe961864b5fe9b0..c64085c86aed3ad8b9b9d17179dcd2e5c6b43779 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -1131,7 +1131,8 @@ GrGradientEffect::GrGradientEffect(GrContext* ctx,
             fCoordTransform.reset(kCoordSet, matrix, fAtlas->getTexture(), params.filterMode());
             fTextureAccess.reset(fAtlas->getTexture(), params);
         } else {
-            SkAutoTUnref<GrTexture> texture(GrRefCachedBitmapTexture(ctx, bitmap, params));
+            SkAutoTUnref<GrTexture> texture(
+                GrRefCachedBitmapTexture(ctx, bitmap, params, SkSourceGammaTreatment::kRespect));
             if (!texture) {
                 return;
             }