add context override of GeometryBufferMapThreshold

src/gpu/GrBufferAllocPool.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrBufferAllocPool_DEFINED
 #define GrBufferAllocPool_DEFINED
 
@@ skipping 110 matching lines @@
     size_t                          fMinBlockSize;
     BufferType                      fBufferType;
 
     SkTArray<BufferBlock>           fBlocks;
     int                             fPreallocBuffersInUse;
     // We attempt to cycle through the preallocated buffers rather than
     // always starting from the first.
     int                             fPreallocBufferStartIdx;
     SkAutoMalloc                    fCpuData;
     void*                           fBufferPtr;
+    size_t                          fGeometryBufferMapThreshold;
 };
 
 class GrVertexBuffer;
 
 /**
  * A GrBufferAllocPool of vertex buffers
  */
 class GrVertexBufferAllocPool : public GrBufferAllocPool {
 public:
     /**
@@ skipping 79 matching lines @@
      */
     void* makeSpace(int indexCount,
                     const GrIndexBuffer** buffer,
                     int* startIndex);
 
 private:
     typedef GrBufferAllocPool INHERITED;
 };
 
 #endif