Port most uses of SkOnce to SkLazyPtr.

include/core/SkPathRef.h

Index: include/core/SkPathRef.h
diff --git a/include/core/SkPathRef.h b/include/core/SkPathRef.h
index 8802714243090edc3fa207a58ffebce8bc356a4d..47a69b7e737aead35ccdfc0a24e1c107a08d6971 100644
--- a/include/core/SkPathRef.h
+++ b/include/core/SkPathRef.h
@@ -418,7 +418,7 @@ private:
     /**
      * Called the first time someone calls CreateEmpty to actually create the singleton.
      */
-    static void CreateEmptyImpl(int/*unused*/);
+    static SkPathRef* CreateEmptyImpl();
 
     void setIsOval(bool isOval) { fIsOval = isOval; }