Add implementation of path ops

src/pathops/SkOpSpan.h

+/*
+ * Copyright 2012 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef SkOpSpan_DEFINED
+#define SkOpSpan_DEFINED
+
+#include "SkPoint.h"
+
+class SkOpSegment;
+
+struct SkOpSpan {
+    SkOpSegment* fOther;
+    SkPoint fPt; // computed when the curves are intersected
+    double fT;
+    double fOtherT; // value at fOther[fOtherIndex].fT
+    int fOtherIndex;  // can't be used during intersection
+    int fWindSum; // accumulated from contours surrounding this one.
+    int fOppSum; // for binary operators: the opposite winding sum
+    int fWindValue; // 0 == canceled; 1 == normal; >1 == coincident
+    int fOppValue; // normally 0 -- when binary coincident edges combine, opp value goes here
+    bool fDone; // if set, this span to next higher T has been processed
+    bool fUnsortableStart; // set when start is part of an unsortable pair
+    bool fUnsortableEnd; // set when end is part of an unsortable pair
+    bool fTiny; // if set, span may still be considered once for edge following
+    bool fLoop; // set when a cubic loops back to this point
+};
+
+#endif