Move chunk expvars into torrent prefix

connection.go

@@ -1204,7 +1204,7 @@ func (cn *connection) rw() io.ReadWriter {
 func (c *connection) receiveChunk(msg *pp.Message) {
 	t := c.t
 	cl := t.cl
-	chunksReceived.Add(1)
+	torrent.Add("chunks received", 1)
 
 	req := newRequestFromMessage(msg)
 
@@ -1212,7 +1212,7 @@ func (c *connection) receiveChunk(msg *pp.Message) {
 	if c.deleteRequest(req) {
 		c.updateRequests()
 	} else {
-		unexpectedChunksReceived.Add(1)
+		torrent.Add("chunks received unexpected", 1)
 	}
 
 	if c.PeerChoked {
@@ -1224,7 +1224,7 @@ func (c *connection) receiveChunk(msg *pp.Message) {
 
 	// Do we actually want this chunk?
 	if !t.wantPiece(req) {
-		unwantedChunksReceived.Add(1)
+		torrent.Add("chunks received unwanted", 1)
 		c.allStats(add(1, func(cs *ConnStats) *Count { return &cs.ChunksReadUnwanted }))
 		return
 	}

global.go

@@ -23,10 +23,6 @@ func defaultPeerExtensionBytes() peerExtensionBytes {
 // I could move a lot of these counters to their own file, but I suspect they
 // may be attached to a Client someday.
 var (
-	unwantedChunksReceived   = expvar.NewInt("chunksReceivedUnwanted")
-	unexpectedChunksReceived = expvar.NewInt("chunksReceivedUnexpected")
-	chunksReceived           = expvar.NewInt("chunksReceived")
-
 	torrent = expvar.NewMap("torrent")
 
 	peersAddedBySource = expvar.NewMap("peersAddedBySource")