add Make variations to return SkImage by sk_sp

include/core/SkShader.h

Index: include/core/SkShader.h
diff --git a/include/core/SkShader.h b/include/core/SkShader.h
index 3e4093645cc2f6ddc301171fc1021f0978293b1a..8b441273b4f0f6bcf83ce6c8c0254187c85c1a5c 100644
--- a/include/core/SkShader.h
+++ b/include/core/SkShader.h
@@ -404,7 +404,7 @@ public:
      *              bounds.
      *  @return     Returns a new shader object. Note: this function never returns null.
     */
-    static sk_sp<SkShader> MakePictureShader(sk_sp<const SkPicture> src, TileMode tmx, TileMode tmy,

[f(malita), 2016/03/10 18:12:15]

Curious whether we dropped const for a particular reason.

[reed1, 2016/03/10 19:12:56]

Tangential for this CL, but I have found it odd (and slightly bad) that we call
picture context, but all other similar objects are not (e.g. all effects,
images, data). I can revert const-ness if you object.

+    static sk_sp<SkShader> MakePictureShader(sk_sp<SkPicture> src, TileMode tmx, TileMode tmy,
                                              const SkMatrix* localMatrix, const SkRect* tile);
 
     /**