by robryk:

If I read and write from/to a buffer in such a way that buffer's length remains bounded,
but it is never empty, the buffer's underlying byte slice will grow unboundedly.

What steps will reproduce the problem?
If possible, include a link to a program on play.golang.org.
http://play.golang.org/p/SsC896Kwd- runs out of memory, instead of running out of time.

What is the expected output?
I would expect the buffer to consume a bounded and small amount of memory, as it happens
when the buffer occasionally runs dry. 

I believe this problem is caused by the bytes.Buffer always allocating a larger buffer
in grow(n); even if the buffer's capacity is larger than twice the required size.