Enable tessellating GPU path renderer.

src/gpu/GrTessellatingPathRenderer.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 "GrTessellatingPathRenderer.h"
 
 #include "GrBatch.h"
@@ skipping 1054 matching lines @@
     Vertex* a;
     Vertex* b;
     front_back_split(*head, &a, &b);
 
     merge_sort(&a);
     merge_sort(&b);
 
     *head = sorted_merge(a, b);
 }
 
+inline void append_vertex(Vertex* v, Vertex** head, Vertex** tail) {
+    insert<Vertex, &Vertex::fPrev, &Vertex::fNext>(v, *tail, NULL, head, tail);
+}
+
+inline void append_vertex_list(Vertex* v, Vertex** head, Vertex** tail) {
+    insert<Vertex, &Vertex::fPrev, &Vertex::fNext>(v, *tail, v->fNext, head, tail);
+}
+
 Vertex* sorted_merge(Vertex* a, Vertex* b) {
-    if (!a) {
-        return b;
-    } else if (!b) {
-        return a;
+    Vertex* head = NULL;
+    Vertex* tail = NULL;
+
+    while (a && b) {
+        if (sweep_lt(a->fPoint, b->fPoint)) {
+            Vertex* next = a->fNext;
+            append_vertex(a, &head, &tail);
+            a = next;
+        } else {
+            Vertex* next = b->fNext;
+            append_vertex(b, &head, &tail);
+            b = next;
+        }
     }
-
-    Vertex* result = NULL;
-
-    if (sweep_lt(a->fPoint, b->fPoint)) {
-        result = a;
-        result->fNext = sorted_merge(a->fNext, b);
-    } else {
-        result = b;
-        result->fNext = sorted_merge(a, b->fNext);
+    if (a) {
+        append_vertex_list(a, &head, &tail);
     }
-    result->fNext->fPrev = result;
-    return result;
+    if (b) {
+        append_vertex_list(b, &head, &tail);
+    }
+    return head;
 }
 
 // Stage 4: Simplify the mesh by inserting new vertices at intersecting edges.
 
 void simplify(Vertex* vertices, SkChunkAlloc& alloc) {
     LOG("simplifying complex polygons\n");
     Edge* activeEdges = NULL;
     for (Vertex* v = vertices; v != NULL; v = v->fNext) {
         if (!v->fFirstEdgeAbove && !v->fFirstEdgeBelow) {
             continue;
@@ skipping 377 matching lines @@
     SkMatrix vmi;
     if (!viewM.invert(&vmi)) {
         return false;
     }
     vmi.mapRect(&clipBounds);
     SkAutoTUnref<GrBatch> batch(TessellatingPathBatch::Create(color, path, viewM, clipBounds));
     target->drawBatch(pipelineBuilder, batch);
 
     return true;
 }