path ops stream-lining

src/pathops/SkOpSpan.cpp

Index: src/pathops/SkOpSpan.cpp
diff --git a/src/pathops/SkOpSpan.cpp b/src/pathops/SkOpSpan.cpp
index 640ba8feb74a0c41dfc5b957edb14295b5b2de30..98165fcfc53c08458d942dfddff78c9a58e468d2 100755
--- a/src/pathops/SkOpSpan.cpp
+++ b/src/pathops/SkOpSpan.cpp
@@ -180,7 +180,9 @@ void SkOpPtT::setDeleted() {
 // please keep this in sync with debugAddOppAndMerge
 // If the added points envelop adjacent spans, merge them in.
 void SkOpSpanBase::addOppAndMerge(SkOpSpanBase* opp) {
-    if (this->ptT()->addOpp(opp->ptT())) {
+    SkOpPtT* oppPrev = this->ptT()->oppPrev(opp->ptT());
+    if (oppPrev) {
+        this->ptT()->addOpp(opp->ptT(), oppPrev);
         this->checkForCollapsedCoincidence();
     }
     // compute bounds of points in span