ssh: soft code internal channel size for testing purposes

Change-Id: I2ee0ed4ba82d2d156a7896551dea04b28cdeceb0
Reviewed-on: https://go-review.googlesource.com/35184
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>

ssh/channel.go

@@ -461,8 +461,8 @@ func (m *mux) newChannel(chanType string, direction channelDirection, extraData
 		pending:          newBuffer(),
 		extPending:       newBuffer(),
 		direction:        direction,
-		incomingRequests: make(chan *Request, 16),
-		msg:              make(chan interface{}, 16),
+		incomingRequests: make(chan *Request, chanSize),
+		msg:              make(chan interface{}, chanSize),
 		chanType:         chanType,
 		extraData:        extraData,
 		mux:              m,