Add SkSourceGammaTreatment enum so we know how to create mips

src/core/SkPictureShader.cpp

Index: src/core/SkPictureShader.cpp
diff --git a/src/core/SkPictureShader.cpp b/src/core/SkPictureShader.cpp
index b6f4d02a55b1cc4a2b4c814d248eee5c8ebb008d..4f584de8a9717971614cd3d1cfaaf1ea8c1eb6e4 100644
--- a/src/core/SkPictureShader.cpp
+++ b/src/core/SkPictureShader.cpp
@@ -322,7 +322,8 @@ const GrFragmentProcessor* SkPictureShader::asFragmentProcessor(
                                                     GrContext* context,
                                                     const SkMatrix& viewM,
                                                     const SkMatrix* localMatrix,
-                                                    SkFilterQuality fq) const {
+                                                    SkFilterQuality fq,
+                                                    bool gammaCorrect) const {
     int maxTextureSize = 0;
     if (context) {
         maxTextureSize = context->caps()->maxTextureSize();
@@ -331,6 +332,6 @@ const GrFragmentProcessor* SkPictureShader::asFragmentProcessor(
     if (!bitmapShader) {
         return nullptr;
     }
-    return bitmapShader->asFragmentProcessor(context, viewM, nullptr, fq);
+    return bitmapShader->asFragmentProcessor(context, viewM, nullptr, fq, gammaCorrect);
 }
 #endif