optimize pathops coverage

Remove unused code from SkOpSegment.cpp and friends.
Add new tests exposed by coverage.
Fix a bug exposed by coverage -- removing the need to detect points that are nearby when intersecting.
Add gyp rule for building coverage flavor on Mac.

R=mtklein@google.com

Author: caryclark@google.com

Review URL: https://codereview.chromium.org/75453003

git-svn-id: http://skia.googlecode.com/svn/trunk@12344 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/pathops/SkOpContour.h b/src/pathops/SkOpContour.h
index 6b412e5..8cedab4 100644
--- a/src/pathops/SkOpContour.h
+++ b/src/pathops/SkOpContour.h
@@ -72,10 +72,9 @@
         return fSegments.count();
     }
 
-    int addT(int segIndex, SkOpContour* other, int otherIndex, const SkPoint& pt, double newT,
-            bool isNear) {
+    int addT(int segIndex, SkOpContour* other, int otherIndex, const SkPoint& pt, double newT) {
         setContainsIntercepts();
-        return fSegments[segIndex].addT(&other->fSegments[otherIndex], pt, newT, isNear);
+        return fSegments[segIndex].addT(&other->fSegments[otherIndex], pt, newT);
     }
 
     int addSelfT(int segIndex, SkOpContour* other, int otherIndex, const SkPoint& pt, double newT) {