path ops -- rewrite angle sort

src/pathops/SkPathOpsPoint.h

Index: src/pathops/SkPathOpsPoint.h
===================================================================
--- src/pathops/SkPathOpsPoint.h	(revision 9425)
+++ src/pathops/SkPathOpsPoint.h	(working copy)
@@ -117,8 +117,8 @@
             return true;
         }
         double inv = 1 / denom;
-        return approximately_equal(fX * inv, a.fX * inv)
-                && approximately_equal(fY * inv, a.fY * inv);
+        return approximately_equal_double(fX * inv, a.fX * inv)
+                && approximately_equal_double(fY * inv, a.fY * inv);
     }
 
     bool approximatelyEqualHalf(const SkDPoint& a) const {
@@ -151,6 +151,13 @@
         return temp.lengthSquared();
     }
 
+    static SkDPoint Mid(const SkDPoint& a, const SkDPoint& b) {
+        SkDPoint result;
+        result.fX = (a.fX + b.fX) / 2;
+        result.fY = (a.fY + b.fY) / 2;
+        return result;
+    }
+
     double moreRoughlyEqual(const SkDPoint& a) const {
         return more_roughly_equal(a.fY, fY) && more_roughly_equal(a.fX, fX);
     }