don't fix winding for empty paths

tests/PathOpsBuilderTest.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "PathOpsExtendedTest.h"
 #include "PathOpsTestCommon.h"
 #include "SkBitmap.h"
@@ skipping 117 matching lines @@
     path.lineTo(59, 11);
     path.lineTo(41, 11);
 
     SkOpBuilder builder;
     builder.add(path, kUnion_SkPathOp);
     SkPath result;
     builder.resolve(&result);
     int pixelDiff = comparePaths(reporter, __FUNCTION__, path, result);
     REPORTER_ASSERT(reporter, pixelDiff == 0);
 }
+
+DEF_TEST(BuilderIssue502792_2, reporter) {
+    SkPath path, pathB;
+    path.setFillType(SkPath::kWinding_FillType);
+    path.addRect(0, 0, 1, 1, SkPath::kCW_Direction);
+    path.addRect(2, 2, 3, 3, SkPath::kCW_Direction);
+    pathB.setFillType(SkPath::kEvenOdd_FillType);
+    pathB.addRect(3, 3, 4, 4, SkPath::kCW_Direction);
+    pathB.addRect(3, 3, 4, 4, SkPath::kCW_Direction);
+    SkOpBuilder builder;
+    builder.add(path, kUnion_SkPathOp);
+    builder.add(pathB, kDifference_SkPathOp);
+    SkPath result;
+    builder.resolve(&result);
+}