update the flow control windows of streams opened in 0-RTT

The server might have increased the initial flow control window. We need
to make sure to inform all streams opened during during the 0-RTT
period.

streams_map_outgoing_generic.go

@@ -178,6 +178,17 @@ func (m *outgoingItemsMap) SetMaxStream(num protocol.StreamNum) {
 	m.unblockOpenSync()
 }
 
+// UpdateSendWindow is called when the peer's transport parameters are received.
+// Only in the case of a 0-RTT handshake will we have open streams at this point.
+// We might need to update the send window, in case the server increased it.
+func (m *outgoingItemsMap) UpdateSendWindow(limit protocol.ByteCount) {
+	m.mutex.Lock()
+	for _, str := range m.streams {
+		str.updateSendWindow(limit)
+	}
+	m.mutex.Unlock()
+}
+
 // unblockOpenSync unblocks the next OpenStreamSync go-routine to open a new stream
 func (m *outgoingItemsMap) unblockOpenSync() {
 	if len(m.openQueue) == 0 {