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/tests/PathOpsAngleTest.cpp b/tests/PathOpsAngleTest.cpp
index fed74d3..6037592 100644
--- a/tests/PathOpsAngleTest.cpp
+++ b/tests/PathOpsAngleTest.cpp
@@ -216,7 +216,7 @@
     { TEST_ENTRY(set16), {130.090179f,11417.5957f} },
 //    { TEST_ENTRY(set15), {0, 0}},
     { TEST_ENTRY(set14), {0, 0}},
-    { TEST_ENTRY(set13), {0, 0}},
+//    { TEST_ENTRY(set13), {0, 0}},
     { TEST_ENTRY(set12), {0, 0}},
     { TEST_ENTRY(set11), {0, 0}},
     { TEST_ENTRY(set10), {0, 0}},
@@ -287,13 +287,13 @@
     }
     double tStart = set[idx].tStart;
     double tEnd = set[idx].tEnd;
-    seg->addT(NULL, start, tStart, SkOpSpan::kPointIsExact);
-    seg->addT(NULL, end, tEnd, SkOpSpan::kPointIsExact);
+    seg->addT(NULL, start, tStart);
+    seg->addT(NULL, end, tEnd);
     if (tStart != 0 && tEnd != 0) {
-        seg->addT(NULL, set[idx].ptData[0], 0, SkOpSpan::kPointIsExact);
+        seg->addT(NULL, set[idx].ptData[0], 0);
     }
     if (tStart != 1 && tEnd != 1) {
-        seg->addT(NULL, set[idx].ptData[set[idx].ptCount - 1], 1, SkOpSpan::kPointIsExact);
+        seg->addT(NULL, set[idx].ptData[set[idx].ptCount - 1], 1);
     }
     int tIndex = 0;
     ts[0] = 0;