Add base types for path ops

src/pathops/SkPathOpsLine.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 SkPathOpsLine_DEFINED
+#define SkPathOpsLine_DEFINED
+
+#include "SkPathOpsPoint.h"
+
+struct SkDLine {
+    SkDPoint fPts[2];
+
+    void set(const SkPoint pts[2]) {
+        fPts[0] = pts[0];
+        fPts[1] = pts[1];
+    }
+
+    const SkDPoint& operator[](int n) const { return fPts[n]; }
+    SkDPoint& operator[](int n) { return fPts[n]; }
+
+//  bool implicitLine(double* slope, double* axisIntercept) const; // uncalled
+//  int reduceOrder(SkDLine* reduced) const; // uncalled
+    double isLeft(const SkDPoint& pt) const;
+    SkDLine subDivide(double t1, double t2) const;
+    static SkDLine SubDivide(const SkPoint a[2], double t1, double t2) {
+        SkDLine line;
+        line.set(a);
+        return line.subDivide(t1, t2);
+    }
+//  double tAt(const SkDPoint& ) const; // uncalled
+    SkDPoint xyAtT(double t) const;
+private:
+    SkDVector tangent() const { return fPts[0] - fPts[1]; }
+};
+
+#endif