Revert 113250 - Add CommandBuffer::SetGetBuffer

Revert 113250 - Add CommandBuffer::SetGetBuffer

As well as remove CommandBuffer::GetRingBuffer and
change CommandBuffer::Initialize

Before this change the service allocated and managed the command buffer.

After this change the client uses CreateTransferBuffer, GetTransferBuffer,
end potentially DeleteTransferBufffer to manage the command buffer.

Another CL will actually make the client delete the command buffer
on demand.

TEST=unit tests and run some samples and a NaCl 3D game
BUG=103989
Review URL: http://codereview.chromium.org/8566059

TBR=gman@chromium.org
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=113255