Better (?) interface for controlling sRGB-ness of mipmaps on GrTexture

Switch to new SkSourceGammaTreatment type. Move to a separate setter,
rather than an optional argument to dirty. Set the flag correctly after
uploading CPU-built mips.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2058143002

Review-Url: https://codereview.chromium.org/2058143002
diff --git a/src/gpu/GrTexturePriv.h b/src/gpu/GrTexturePriv.h
index 762890f..c4e6538 100644
--- a/src/gpu/GrTexturePriv.h
+++ b/src/gpu/GrTexturePriv.h
@@ -29,8 +29,8 @@
         return 0 != (fTexture->fDesc.fFlags & flags);
     }
 
-    void dirtyMipMaps(bool mipMapsDirty, bool sRGBCorrect = false) {
-        fTexture->dirtyMipMaps(mipMapsDirty, sRGBCorrect);
+    void dirtyMipMaps(bool mipMapsDirty) {
+        fTexture->dirtyMipMaps(mipMapsDirty);
     }
 
     bool mipMapsAreDirty() const {
@@ -49,9 +49,10 @@
         return fTexture->fMaxMipMapLevel;
     }
 
-    bool mipMapsAreSRGBCorrect() const {
-        return fTexture->fMipMapsAreSRGBCorrect;
+    void setGammaTreatment(SkSourceGammaTreatment gammaTreatment) const {
+        fTexture->fGammaTreatment = gammaTreatment;
     }
+    SkSourceGammaTreatment gammaTreatment() const { return fTexture->fGammaTreatment; }
 
     static void ComputeScratchKey(const GrSurfaceDesc&, GrScratchKey*);