Add SkSourceGammaTreatment enum so we know how to create mips

src/image/SkImage_Gpu.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImage_Gpu_DEFINED
 #define SkImage_Gpu_DEFINED
 
@@ skipping 21 matching lines @@
 
     void applyBudgetDecision() const {
         if (SkBudgeted::kYes == fBudgeted) {
             fTexture->resourcePriv().makeBudgeted();
         } else {
             fTexture->resourcePriv().makeUnbudgeted();
         }
     }
 
     bool getROPixels(SkBitmap*, CachingHint) const override;
-    GrTexture* asTextureRef(GrContext* ctx, const GrTextureParams& params) const override;
+    GrTexture* asTextureRef(GrContext* ctx, const GrTextureParams& params,
+                            SkSourceGammaTreatment) const override;
     sk_sp<SkImage> onMakeSubset(const SkIRect&) const override;
 
     GrTexture* peekTexture() const override { return fTexture; }
     bool isOpaque() const override;
     bool onReadPixels(const SkImageInfo&, void* dstPixels, size_t dstRowBytes,
                       int srcX, int srcY, CachingHint) const override;
 
     sk_sp<SkSurface> onNewSurface(const SkImageInfo& info) const override {
         return SkSurface::MakeRenderTarget(fTexture->getContext(), SkBudgeted::kNo, info);
     }
 
     bool asBitmapForImageFilters(SkBitmap* bitmap) const override;
 
 private:
     SkAutoTUnref<GrTexture>     fTexture;
     const SkAlphaType           fAlphaType;
     const SkBudgeted            fBudgeted;
     mutable SkAtomic<bool>      fAddedRasterVersionToCache;
 
 
     typedef SkImage_Base INHERITED;
 };
 
 #endif