fix fuzzer bug

Fix another fuzzer bug.

Some PathOps asserts only make sense if the incoming data is
well-behaved. Well-behaved tests set debugging state to
trigger these additional asserts.

Formalize this by creating macros similar to SkASSERT that
check to see if the assert should be skipped.

TBR=reed@google.com
BUG=629962
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2169863002

Review-Url: https://codereview.chromium.org/2169863002
diff --git a/src/pathops/SkOpSegment.h b/src/pathops/SkOpSegment.h
index 55e67a5d..7cf4b26 100644
--- a/src/pathops/SkOpSegment.h
+++ b/src/pathops/SkOpSegment.h
@@ -186,7 +186,7 @@
     double distSq(double t, const SkOpAngle* opp) const;
 
     bool done() const {
-        SkASSERT(this->globalState()->debugSkipAssert() || fDoneCount <= fCount);
+        SkOPASSERT(fDoneCount <= fCount);
         return fDoneCount == fCount;
     }