Comment 13 for bug 1441553

potential solutions:
1) "new buffer semantics" has better client/server synchronization between the number of buffers in the system, so the problem will go away when the client becomes aware of how many buffers are in the swapping chain.
2) increase mf::client_buffer_cache_size to 4. This is slightly disadventageous because it doesn't solve the problem outright (there can be more than one overallocation), and leaves buffers lingering.