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..185e4ef2c933e1c69676a2f07b70c386cd3e5284 100644
--- a/gm/yuvtorgbeffect.cpp
+++ b/gm/yuvtorgbeffect.cpp
@@ -82,11 +82,14 @@ protected:
 
         SkAutoTUnref<GrTexture> texture[3];
         texture[0].reset(GrRefCachedBitmapTexture(context, fBmp[0],
-                                                  GrTextureParams::ClampBilerp()));
+                                                  GrTextureParams::ClampBilerp(),
+                                                  SkSourceGammaTreatment::kRespect));
         texture[1].reset(GrRefCachedBitmapTexture(context, fBmp[1],
-                                                  GrTextureParams::ClampBilerp()));
+                                                  GrTextureParams::ClampBilerp(),
+                                                  SkSourceGammaTreatment::kRespect));
         texture[2].reset(GrRefCachedBitmapTexture(context, fBmp[2],
-                                                  GrTextureParams::ClampBilerp()));
+                                                  GrTextureParams::ClampBilerp(),
+                                                  SkSourceGammaTreatment::kRespect));
 
         if (!texture[0] || !texture[1] || !texture[2]) {
             return;