Tessellator: better fix for reused-edges issue.

src/gpu/GrTessellator.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrTessellator.h"
 
 #include "GrPathUtils.h"
@@ skipping 342 matching lines @@
             , fNext(nullptr) {
             this->addEdge(edge);
         }
         Side          fSide;
         Edge*         fFirstEdge;
         Edge*         fLastEdge;
         MonotonePoly* fPrev;
         MonotonePoly* fNext;
         void addEdge(Edge* edge) {
             if (fSide == kRight_Side) {
-                if (edge->fUsedInRightPoly) {
-                    return;
-                }
+                SkASSERT(!edge->fUsedInRightPoly);
                 list_insert<Edge, &Edge::fRightPolyPrev, &Edge::fRightPolyNext>(
                     edge, fLastEdge, nullptr, &fFirstEdge, &fLastEdge);
                 edge->fUsedInRightPoly = true;
             } else {
-                if (edge->fUsedInLeftPoly) {
-                    return;
-                }
+                SkASSERT(!edge->fUsedInLeftPoly);
                 list_insert<Edge, &Edge::fLeftPolyPrev, &Edge::fLeftPolyNext>(
                     edge, fLastEdge, nullptr, &fFirstEdge, &fLastEdge);
                 edge->fUsedInLeftPoly = true;
             }
         }
 
         SkPoint* emit(SkPoint* data) {
             Edge* e = fFirstEdge;
             e->fTop->fPrev = e->fTop->fNext = nullptr;
             VertexList vertices;
@@ skipping 33 matching lines @@
                 }
             }
             return data;
         }
     };
     Poly* addEdge(Edge* e, Side side, SkChunkAlloc& alloc) {
         LOG("addEdge (%g -> %g) to poly %d, %s side\n",
                e->fTop->fID, e->fBottom->fID, fID, side == kLeft_Side ? "left" : "right");
         Poly* partner = fPartner;
         Poly* poly = this;
+        if (side == kRight_Side) {
+            if (e->fUsedInRightPoly) {
+                return this;
+            }
+        } else {
+            if (e->fUsedInLeftPoly) {
+                return this;
+            }
+        }
         if (partner) {
             fPartner = partner->fPartner = nullptr;
         }
         if (!fTail) {
             fHead = fTail = ALLOC_NEW(MonotonePoly, (e, side), alloc);
             fCount += 2;
         } else if (e->fBottom == fTail->fLastEdge->fBottom) {
             return poly;
         } else if (side == fTail->fSide) {
             fTail->addEdge(e);
@@ skipping 1015 matching lines @@
         }
     }
     int actualCount = static_cast<int>(vertsEnd - *verts);
     SkASSERT(actualCount <= count);
     SkASSERT(pointsEnd - points == actualCount);
     delete[] points;
     return actualCount;
 }
 
 } // namespace