[skottie] Add support for inverse mask paths

TBR=
Change-Id: I442033b2e82777c90ee497d8a5b2310af1d2e631
Reviewed-on: https://skia-review.googlesource.com/123840
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 7486502..194efe7 100644
--- a/experimental/skottie/Skottie.cpp
+++ b/experimental/skottie/Skottie.cpp
@@ -949,19 +949,16 @@
         if (!m.isObject())
             continue;
 
-        const auto inverted = ParseDefault(m["inv"], false);
-        // TODO
-        if (inverted) {
-            LogFail(m, "Unsupported inverse mask");
-            continue;
-        }
-
         auto mask_path = AttachPath(m["pt"], ctx);
         if (!mask_path) {
             LogFail(m, "Could not parse mask path");
             continue;
         }
 
+        mask_path->setFillType(ParseDefault(m["inv"], false)
+            ? SkPath::kInverseWinding_FillType
+            : SkPath::kWinding_FillType);
+
         SkString mode;
         if (!Parse(m["mode"], &mode) ||
             mode.size() != 1 ||