Make FencedAlloctor fail on size = 0.

gpu/command_buffer/client/fenced_allocator.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.
 
 // This file contains the definition of the FencedAllocator class.
 
 #ifndef GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_
 #define GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_
 
 #include <vector>
@@ skipping 114 matching lines @@
   // NOTE: this will invalidate block indices.
   BlockIndex WaitForTokenAndFreeBlock(BlockIndex index);
 
   // Allocates a block of memory inside a given block, splitting it in two
   // (unless that block is of the exact requested size).
   // NOTE: this will invalidate block indices.
   // Returns the offset of the allocated block (NOTE: this is different from
   // the other functions that return a block index).
   Offset AllocInBlock(BlockIndex index, unsigned int size);
 
+  // Frees allocations of size = 0.
+  void FreeZeroAlloc(FencedAllocator::Offset offset);
+
   CommandBufferHelper *helper_;
   Container blocks_;
+  Offset zero_offset_;
+  std::vector<bool> zero_allocs_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FencedAllocator);
 };
 
 // This class functions just like FencedAllocator, but its API uses pointers
 // instead of offsets.
 class FencedAllocatorWrapper {
  public:
   FencedAllocatorWrapper(unsigned int size,
                          CommandBufferHelper* helper,
@@ skipping 98 matching lines @@
 
  private:
   FencedAllocator allocator_;
   void* base_;
   DISALLOW_IMPLICIT_CONSTRUCTORS(FencedAllocatorWrapper);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_