Add SkSourceGammaTreatment enum so we know how to create mips

gm/yuvtorgbeffect.cpp

Index: gm/yuvtorgbeffect.cpp
diff --git a/gm/yuvtorgbeffect.cpp b/gm/yuvtorgbeffect.cpp
index 40a2f03f27e223f50ed04541b6e9e9f9d9165311..f0c0955570f255aeb7f5cf25405cd5b783e7f3f9 100644
--- a/gm/yuvtorgbeffect.cpp
+++ b/gm/yuvtorgbeffect.cpp
@@ -82,11 +82,11 @@ protected:
 
         SkAutoTUnref<GrTexture> texture[3];
         texture[0].reset(GrRefCachedBitmapTexture(context, fBmp[0],
-                                                  GrTextureParams::ClampBilerp()));
+                                                  GrTextureParams::ClampBilerp(), false));
         texture[1].reset(GrRefCachedBitmapTexture(context, fBmp[1],
-                                                  GrTextureParams::ClampBilerp()));
+                                                  GrTextureParams::ClampBilerp(), false));
         texture[2].reset(GrRefCachedBitmapTexture(context, fBmp[2],
-                                                  GrTextureParams::ClampBilerp()));
+                                                  GrTextureParams::ClampBilerp(), false));
 
         if (!texture[0] || !texture[1] || !texture[2]) {
             return;