Batch multiple single NVPR draw paths to instanced draws

src/gpu/batches/GrBatch.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 GrBatch_DEFINED
 #define GrBatch_DEFINED
 
@@ skipping 10 matching lines @@
 
 /**
  * GrBatch is the base class for all Ganesh deferred geometry generators.  To facilitate
  * reorderable batching, Ganesh does not generate geometry inline with draw calls.  Instead, it
  * captures the arguments to the draw and then generates the geometry on demand.  This gives GrBatch
  * subclasses complete freedom to decide how / what they can batch.
  *
  * Batches are created when GrContext processes a draw call. Batches of the same  subclass may be
  * merged using combineIfPossible. When two batches merge, one takes on the union of the data
  * and the other is left empty. The merged batch becomes responsible for drawing the data from both
- * the original batches.
+ * the original batches. The merged patch may ref the other batch, if this is more efficient than
+ * moving the data from the other batch to the merged batch.
  *
  * If there are any possible optimizations which might require knowing more about the full state of
  * the draw, ie whether or not the GrBatch is allowed to tweak alpha for coverage, then this
  * information will be communicated to the GrBatch prior to geometry generation.
  *
  * The bounds of the batch must contain all the vertices in device space *irrespective* of the clip.
  * The bounds are used in determining which clip elements must be applied and thus the bounds cannot
  * in turn depend upon the clip.
  */
 #define GR_BATCH_SPEW 0
@@ skipping 116 matching lines @@
 
     SkDEBUGCODE(bool                    fUsed;)
     const uint32_t                      fClassID;
     static uint32_t GenBatchID() { return GenID(&gCurrBatchUniqueID); }
     mutable uint32_t                    fUniqueID;
     static int32_t                      gCurrBatchUniqueID;
     static int32_t                      gCurrBatchClassID;
 };
 
 #endif