Revert "Revert "move onto new factories for SkMatrix""

This reverts commit c80ee456adf664c4a62fa2ccaeaf157c723ed656.

fix: update flutter's gn file to add guard

Change-Id: Iac5171c8475d9a862d06255dab1c6f38f10de2f2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/291361
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/docs/examples/blur_alpha_img.cpp b/docs/examples/blur_alpha_img.cpp
index 880f018..2d00ace 100644
--- a/docs/examples/blur_alpha_img.cpp
+++ b/docs/examples/blur_alpha_img.cpp
@@ -13,7 +13,7 @@
         path.lineTo(pts[i] * scale, pts[i + 1] * scale);
     }
     path.close();
-    SkMatrix matrix = SkMatrix::MakeScale(4 * scale);
+    SkMatrix matrix = SkMatrix::Scale(4 * scale, 4 * scale);
     SkPaint paint;
     paint.setPathEffect(SkPath2DPathEffect::Make(matrix, path));
     paint.setAntiAlias(true);