Broke GrTessellatingPathRenderer's tessellator out into a separate file.

src/gpu/GrTessellator.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrTessellator_DEFINED
+#define GrTessellator_DEFINED
+
+#include "SkChunkAlloc.h"
+#include "GrPathRenderer.h"
+
+/**
+ * Provides utility functions for converting paths to a collection of triangles.
+ */
+
+#define TESSELLATOR_WIREFRAME 0
+
+namespace GrTessellator {
+
+struct Poly;
+struct Edge;
+struct Vertex;
+
+struct EdgeList {
+    EdgeList() : fHead(nullptr), fTail(nullptr) {}
+    Edge* fHead;
+    Edge* fTail;
+};
+
+struct Edge {

[Stephen White, 2016/01/05 15:59:04]

Does this (and EdgeList) need to be public? It only seems to be used in
GrTessellator.cpp. But maybe I missed something.

[ethannicholas, 2016/01/05 16:09:22]

It did at one point, but you are of course correct that it does not need to be
anymore. My bad!

+    Edge(Vertex* top, Vertex* bottom, int winding)
+        : fTop(top)
+        , fBottom(bottom)
+        , fWinding(winding)
+        , fLeft(nullptr)
+        , fRight(nullptr)
+        , fPrevEdgeAbove(nullptr)
+        , fNextEdgeAbove(nullptr)
+        , fPrevEdgeBelow(nullptr)
+        , fNextEdgeBelow(nullptr)
+        , fLeftPoly(nullptr)
+        , fRightPoly(nullptr) {
+            recompute();
+        }
+    Vertex* fTop;          // The top vertex in vertex-sort-order (sweep_lt).
+    Vertex* fBottom;       // The bottom vertex in vertex-sort-order.
+    int    fWinding;       // 1 == edge goes downward; -1 = edge goes upward.
+    Edge*  fLeft;          // The linked list of edges in the active edge list.
+    Edge*  fRight;         // "
+    Edge*  fPrevEdgeAbove; // The linked list of edges in the bottom Vertex's "edges above".
+    Edge*  fNextEdgeAbove; // "
+    Edge*  fPrevEdgeBelow; // The linked list of edges in the top Vertex's "edges below".
+    Edge*  fNextEdgeBelow; // "
+    Poly*  fLeftPoly;      // The Poly to the left of this edge, if any.
+    Poly*  fRightPoly;     // The Poly to the right of this edge, if any.
+    double fDX;            // The line equation for this edge, in implicit form.
+    double fDY;            // fDY * x + fDX * y + fC = 0, for point (x, y) on the line.
+    double fC;
+    double dist(const SkPoint& p) const;
+    bool isRightOf(Vertex* v) const;
+    bool isLeftOf(Vertex* v) const;
+    void recompute();
+    bool intersect(const Edge& other, SkPoint* p);
+    bool isActive(EdgeList* activeEdges) const;
+};
+
+struct WindingVertex {
+    SkPoint fPos;
+    int fWinding;
+};
+
+// creates an array of (point, winding) vertices and sets the 'verts' out parameter to point to it. 
+// CALLER IS RESPONSIBLE for deleting this buffer to avoid a memory leak!
+int PathToVertices(const SkPath& path, SkScalar tolerance, const SkRect& clipBounds, 
+                   WindingVertex** verts);
+
+int PathToTriangles(const SkPath& path, SkScalar tolerance, const SkRect& clipBounds, 
+                    GrResourceProvider* resourceProvider, 
+                    SkAutoTUnref<GrVertexBuffer>& vertexBuffer, bool canMapVB, bool* isLinear);
+
+}
+
+#endif