Batch multiple single NVPR draw paths to instanced draws

src/gpu/batches/GrDrawPathBatch.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 GrDrawPathBatch_DEFINED
 #define GrDrawPathBatch_DEFINED
 
@@ skipping 58 matching lines @@
     }
 
     const char* name() const override { return "DrawPath"; }
 
     SkString dumpInfo() const override;
 
 private:
     GrDrawPathBatch(const SkMatrix& viewMatrix, GrColor color, GrPathRendering::FillType fill,
                     const GrPath* path)
         : INHERITED(ClassID(), viewMatrix, color, fill)
-        , fPath(path) {
+        , fPath(path)
+        , fNext(nullptr)
+        , fLastSlot(&fNext)
+        , fTotalPathCount(1) {
         fBounds = path->getBounds();
         viewMatrix.mapRect(&fBounds);
+        fPathBounds = fBounds;
     }
-
-    bool onCombineIfPossible(GrBatch* t, const GrCaps& caps) override { return false; }
+    static bool ListBoundsIntersects(const GrDrawPathBatch* a, const GrDrawPathBatch* b);
+    bool onCombineIfPossible(GrBatch* t, const GrCaps& caps) override;
 
     void onPrepare(GrBatchFlushState*) override {}
 
     void onDraw(GrBatchFlushState* state) override;
 
     GrPendingIOResource<const GrPath, kRead_GrIOType> fPath;
-
+    SkRect fPathBounds;
+    sk_sp<GrDrawPathBatch> fNext;       // Batch union is made with a linked list of batch nodes.
+    sk_sp<GrDrawPathBatch>* fLastSlot;  // Points to the fNext of the last batch in the batch list.
+    int fTotalPathCount;
     typedef GrDrawPathBatchBase INHERITED;
 };
 
 // Template this if we decide to support index types other than 16bit
 class GrDrawPathRangeBatch final : public GrDrawPathBatchBase {
 public:
     typedef GrPathRendering::PathTransformType TransformType;
 
     DEFINE_BATCH_CLASS_ID
 
@@ skipping 98 matching lines @@
 
     PendingPathRange    fPathRange;
     DrawList            fDraws;
     int                 fTotalPathCount;
     SkScalar            fScale;
 
     typedef GrDrawPathBatchBase INHERITED;
 };
 
 #endif