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

gpu/command_buffer/client/transfer_buffer.h

Index: gpu/command_buffer/client/transfer_buffer.h
diff --git a/gpu/command_buffer/client/transfer_buffer.h b/gpu/command_buffer/client/transfer_buffer.h
index 5f6623e05124e28dbb8f3985d9c3c0972367ee11..c0c2ba040cd812f2cf5f495213144a3995e62bf5 100644
--- a/gpu/command_buffer/client/transfer_buffer.h
+++ b/gpu/command_buffer/client/transfer_buffer.h
@@ -59,6 +59,8 @@ class GPU_EXPORT TransferBufferInterface {
   virtual unsigned int GetSize() const = 0;
 
   virtual unsigned int GetFreeSize() const = 0;
+
+  virtual base::SharedMemory* GetSharedMemory() const = 0;
 };
 
 // Class that manages the transfer buffer.
@@ -86,6 +88,7 @@ class GPU_EXPORT TransferBuffer : public TransferBufferInterface {
   void FreePendingToken(void* p, unsigned int token) override;
   unsigned int GetSize() const override;
   unsigned int GetFreeSize() const override;
+  base::SharedMemory* GetSharedMemory() const override;
 
   // These are for testing.
   unsigned int GetCurrentMaxAllocationWithoutRealloc() const;