combine vertical overlapping edges

src/core/SkEdgeBuilder.h

Index: src/core/SkEdgeBuilder.h
diff --git a/src/core/SkEdgeBuilder.h b/src/core/SkEdgeBuilder.h
index 625465b8a6b28357ede6e6524d7a52ca14c5291e..047460d4fef06e301a9c7a91d827ac148398eb2b 100644
--- a/src/core/SkEdgeBuilder.h
+++ b/src/core/SkEdgeBuilder.h
@@ -27,6 +27,15 @@ public:
     SkEdge** edgeList() { return fEdgeList; }
 
 private:
+    enum Combine {
+        kNo_Combine,
+        kPartial_Combine,
+        kTotal_Combine
+    };
+
+    static Combine CombineVertical(const SkEdge* edge, SkEdge* last);
+    Combine checkVertical(const SkEdge* edge, SkEdge** edgePtr);
+
     SkChunkAlloc        fAlloc;
     SkTDArray<SkEdge*>  fList;