Enable asynchronous glReadPixels on Windows.

gpu/command_buffer/client/mapped_memory.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GPU_COMMAND_BUFFER_CLIENT_MAPPED_MEMORY_H_
 #define GPU_COMMAND_BUFFER_CLIENT_MAPPED_MEMORY_H_
 
 #include <stdint.h>
 
 #include "base/bind.h"
@@ skipping 117 matching lines @@
                       const base::Closure& poll_callback,
                       size_t unused_memory_reclaim_limit);
 
   ~MappedMemoryManager();
 
   unsigned int chunk_size_multiple() const {
     return chunk_size_multiple_;
   }
 
   void set_chunk_size_multiple(unsigned int multiple) {
+    DCHECK_GE(multiple, FencedAllocator::kAllocAlignment);
     chunk_size_multiple_ = multiple;
   }
 
   // Allocates a block of memory
   // Parameters:
   //   size: size of memory to allocate.
   //   shm_id: pointer to variable to receive the shared memory id.
   //   shm_offset: pointer to variable to receive the shared memory offset.
   // Returns:
   //   pointer to allocated block of memory. NULL if failure.
@@ skipping 46 matching lines @@
   MemoryChunkVector chunks_;
   size_t allocated_memory_;
   size_t max_free_bytes_;
 
   DISALLOW_COPY_AND_ASSIGN(MappedMemoryManager);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_MAPPED_MEMORY_H_
-