api: Implement RelationUnitsWatcher in client API

state/api/apiclient.go

 // Copyright 2012, 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 package api
 
 import (
         "code.google.com/p/go.net/websocket"
         "crypto/tls"
         "crypto/x509"
         "launchpad.net/juju-core/cert"
         "launchpad.net/juju-core/log"
         "launchpad.net/juju-core/rpc"
         "launchpad.net/juju-core/rpc/jsoncodec"
         "launchpad.net/juju-core/state/api/params"
         "launchpad.net/juju-core/utils"
         "time"
 )
 
 // PingPeriod defines how often the internal connection health check
 // will run. It's a variable so it can be changed in tests.
 var PingPeriod = 1 * time.Minute
 
 type State struct {
         client *rpc.Conn
         conn   *websocket.Conn
 
+        // authTag holds the authenticated entity's tag after login.
+        authTag string
+
         // broken is a channel that gets closed when the connection is
         // broken.
         broken chan struct{}
 }
 
 // Info encapsulates information about a server holding juju state and
 // can be used to make a connection to it.
 type Info struct {
         // Addrs holds the addresses of the state servers.
         Addrs []string
@@ skipping 127 matching lines @@
 func (s *State) Broken() <-chan struct{} {
         return s.broken
 }
 
 // RPCClient returns the RPC client for the state, so that testing
 // functions can tickle parts of the API that the conventional entry
 // points don't reach. This is exported for testing purposes only.
 func (s *State) RPCClient() *rpc.Conn {
         return s.client
 }