Add SkSourceGammaTreatment enum so we know how to create mips

src/core/SkLocalMatrixShader.h

Index: src/core/SkLocalMatrixShader.h
diff --git a/src/core/SkLocalMatrixShader.h b/src/core/SkLocalMatrixShader.h
index 8edea40d05bd1d896bcca7d31ef86bb96ddb4716..18a20c8bdf2e3976e56807f210a3308eeabfeffa 100644
--- a/src/core/SkLocalMatrixShader.h
+++ b/src/core/SkLocalMatrixShader.h
@@ -26,12 +26,13 @@ public:
 #if SK_SUPPORT_GPU
     const GrFragmentProcessor* asFragmentProcessor(GrContext* context, const SkMatrix& viewM,
                                                    const SkMatrix* localMatrix,
-                                                   SkFilterQuality fq) const override {
+                                                   SkFilterQuality fq,
+                                                   bool gammaCorrect) const override {
         SkMatrix tmp = this->getLocalMatrix();
         if (localMatrix) {
             tmp.preConcat(*localMatrix);
         }
-        return fProxyShader->asFragmentProcessor(context, viewM, &tmp, fq);
+        return fProxyShader->asFragmentProcessor(context, viewM, &tmp, fq, gammaCorrect);
     }
 #endif