Delay creation of cpu-side buffer memory until actually needed

src/gpu/GrBufferAllocPool.cpp

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrBufferAllocPool.h"
 #include "GrBuffer.h"
@@ skipping 60 matching lines @@
     VALIDATE();
     this->deleteBlocks();
     sk_free(fCpuData);
     fGpu->unref();
 }
 
 void GrBufferAllocPool::reset() {
     VALIDATE();
     fBytesInUse = 0;
     this->deleteBlocks();
-
-    // we may have created a large cpu mirror of a large VB. Reset the size to match our minimum.
-    this->resetCpuData(fMinBlockSize);
-
+    this->resetCpuData(0);      // delete all the cpu-side memory
     VALIDATE();
 }
 
 void GrBufferAllocPool::unmap() {
     VALIDATE();
 
     if (fBufferPtr) {
         BufferBlock& block = fBlocks.back();
         if (block.fBuffer->isMapped()) {
             UNMAP_BUFFER(block);
@@ skipping 270 matching lines @@
     size_t offset = 0; // assign to suppress warning
     void* ptr = INHERITED::makeSpace(indexCount * sizeof(uint16_t),
                                      sizeof(uint16_t),
                                      buffer,
                                      &offset);
 
     SkASSERT(0 == offset % sizeof(uint16_t));
     *startIndex = static_cast<int>(offset / sizeof(uint16_t));
     return ptr;
 }