[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

gpu/ipc/client/gpu_memory_buffer_impl_shared_memory.h

 // Copyright 2014 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_IPC_CLIENT_GPU_MEMORY_BUFFER_IMPL_SHARED_MEMORY_H_
 #define GPU_IPC_CLIENT_GPU_MEMORY_BUFFER_IMPL_SHARED_MEMORY_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 39 matching lines @@
                                           gfx::GpuMemoryBufferHandle* handle);
 
   // Overridden from gfx::GpuMemoryBuffer:
   bool Map() override;
   void* memory(size_t plane) override;
   void Unmap() override;
   int stride(size_t plane) const override;
   gfx::GpuMemoryBufferHandle GetHandle() const override;
   base::trace_event::MemoryAllocatorDumpGuid GetGUIDForTracing(
       uint64_t tracing_process_id) const override;
+  base::SharedMemory* GetSharedMemory() override;
 
  private:
   GpuMemoryBufferImplSharedMemory(
       gfx::GpuMemoryBufferId id,
       const gfx::Size& size,
       gfx::BufferFormat format,
       const DestructionCallback& callback,
       std::unique_ptr<base::SharedMemory> shared_memory,
       size_t offset,
       int stride);
 
   std::unique_ptr<base::SharedMemory> shared_memory_;
   size_t offset_;
   int stride_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuMemoryBufferImplSharedMemory);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_IPC_CLIENT_GPU_MEMORY_BUFFER_IMPL_SHARED_MEMORY_H_