Add back parts of reverted changes that were not concerned with child agent caching.

This adds ScenePresence to IClientAPI.SceneAgent earlier on in the add client process so that its information is available to EventManager.OnNewClient() and OnClientLogin()
Also add a code comment as to why we're caching friend information for child agents.

OpenSim/Framework/IClientAPI.cs

@@ -710,7 +710,7 @@ namespace OpenSim.Framework
         /// The scene agent for this client.  This will only be set if the client has an agent in a scene (i.e. if it
         /// is connected).
         /// </summary>
-        ISceneAgent SceneAgent { get; }
+        ISceneAgent SceneAgent { get; set; }
 
         UUID SessionId { get; }
 

OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs

@@ -385,7 +385,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             set { m_startpos = value; }
         }
         public UUID AgentId { get { return m_agentId; } }
-        public ISceneAgent SceneAgent { get; private set; }
+        public ISceneAgent SceneAgent { get; set; }
         public UUID ActiveGroupId { get { return m_activeGroupID; } }
         public string ActiveGroupName { get { return m_activeGroupName; } }
         public ulong ActiveGroupPowers { get { return m_activeGroupPowers; } }
@@ -698,7 +698,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
         public virtual void Start()
         {
-            SceneAgent = m_scene.AddNewClient(this, PresenceType.User);
+            m_scene.AddNewClient(this, PresenceType.User);
 
             RefreshGroupMembership();
         }

OpenSim/Region/CoreModules/Avatar/Friends/FriendsModule.cs

@@ -261,6 +261,9 @@ namespace OpenSim.Region.CoreModules.Avatar.Friends
             client.OnTerminateFriendship += (thisClient, agentID, exfriendID) => RemoveFriendship(thisClient, exfriendID);
             client.OnGrantUserRights += OnGrantUserRights;
 
+            // We need to cache information for child agents as well as root agents so that friend edit/move/delete
+            // permissions will work across borders where both regions are on different simulators.
+            //
             // Do not do this asynchronously.  If we do, then subsequent code can outrace CacheFriends() and
             // return misleading results from the still empty friends cache.
             // If we absolutely need to do this asynchronously, then a signalling mechanism is needed so that calls

OpenSim/Region/Framework/Scenes/EventManager.cs

@@ -71,6 +71,7 @@ namespace OpenSim.Region.Framework.Scenes
         /// Triggered when a new client is added to the scene.
         /// </summary>
         /// <remarks>
+        /// This is triggered for both child and root agent client connections.
         /// Triggered before OnClientLogin.
         /// </remarks>
         public event OnNewClientDelegate OnNewClient;
@@ -191,7 +192,7 @@ namespace OpenSim.Region.Framework.Scenes
         public delegate void ClientClosed(UUID clientID, Scene scene);
 
         /// <summary>
-        /// Fired when a client is removed from a scene.
+        /// Fired when a client is removed from a scene whether it's a child or a root agent.
         /// </summary>
         /// <remarks>
         /// At the point of firing, the scene still contains the client's scene presence.

OpenSim/Region/Framework/Scenes/Scene.cs

@@ -2675,6 +2675,10 @@ namespace OpenSim.Region.Framework.Scenes
                     sp.IsChildAgent ? "child" : "root", sp.Name, RegionInfo.RegionName);
             }
 
+            // We must set this here so that TriggerOnNewClient and TriggerOnClientLogin can determine whether the
+            // client is for a root or child agent.
+            client.SceneAgent = sp;
+
             m_LastLogin = Util.EnvironmentTickCount();
 
             // Cache the user's name

OpenSim/Region/OptionalModules/Agent/InternetRelayClientView/Server/IRCClientView.cs

@@ -55,7 +55,7 @@ namespace OpenSim.Region.OptionalModules.Agent.InternetRelayClientView.Server
 
         private UUID m_agentID = UUID.Random();
 
-        public ISceneAgent SceneAgent { get; private set; }
+        public ISceneAgent SceneAgent { get; set; }
 
         private string m_username;
         private string m_nick;
@@ -895,7 +895,7 @@ namespace OpenSim.Region.OptionalModules.Agent.InternetRelayClientView.Server
 
         public void Start()
         {
-            SceneAgent = m_scene.AddNewClient(this, PresenceType.User);
+            m_scene.AddNewClient(this, PresenceType.User);
 
             // Mimicking LLClientView which gets always set appearance from client.
             AvatarAppearance appearance;

OpenSim/Region/OptionalModules/World/NPC/NPCAvatar.cs

@@ -69,7 +69,7 @@ namespace OpenSim.Region.OptionalModules.World.NPC
             get { return m_ownerID; }
         }
 
-        public ISceneAgent SceneAgent { get { throw new NotImplementedException(); } }
+        public ISceneAgent SceneAgent { get; set; }
 
         public void Say(string message)
         {

OpenSim/Tests/Common/Mock/TestClient.cs

@@ -327,7 +327,7 @@ namespace OpenSim.Tests.Common.Mock
         /// </value>
         private UUID m_agentId;
 
-        public ISceneAgent SceneAgent { get { throw new NotImplementedException(); } }
+        public ISceneAgent SceneAgent { get; set; }
 
         /// <value>
         /// The last caps seed url that this client was given.