[skottie] Anti-alias masks

TBR=

Change-Id: I16eca80b515fde8ad87a79c01ffd0ea2b3e31259
Reviewed-on: https://skia-review.googlesource.com/101740
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/experimental/skottie/Skottie.cpp b/experimental/skottie/Skottie.cpp
index 1ac8f7d..aee1210 100644
--- a/experimental/skottie/Skottie.cpp
+++ b/experimental/skottie/Skottie.cpp
@@ -902,6 +902,7 @@
         }
 
         auto mask_paint = sksg::Color::Make(SK_ColorBLACK);
+        mask_paint->setAntiAlias(true);
         mask_paint->setBlendMode(MaskBlendMode(mode.c_str()[0]));
         BindProperty<ScalarValue>(m["o"], &ctx->fAnimators,
             [mask_paint](const ScalarValue& o) { mask_paint->setOpacity(o * 0.01f); });