Add LoadAborted() event

osu.Game/Online/Multiplayer/IMultiplayerClient.cs

@@ -93,10 +93,15 @@ namespace osu.Game.Online.Multiplayer
         Task UserModsChanged(int userId, IEnumerable<APIMod> mods);
 
         /// <summary>
-        /// Signals that a match is to be started. This will *only* be sent to clients which are to begin loading at this point.
+        /// Signals that the match is starting and the loading of gameplay should be started. This will *only* be sent to clients which are to begin loading at this point.
         /// </summary>
         Task LoadRequested();
 
+        /// <summary>
+        /// Signals that loading of gameplay is to be aborted.
+        /// </summary>
+        Task LoadAborted();
+
         /// <summary>
         /// Signals that gameplay has started.
         /// All users in the <see cref="MultiplayerUserState.Loaded"/> or <see cref="MultiplayerUserState.ReadyForGameplay"/> states should begin gameplay as soon as possible.

osu.Game/Online/Multiplayer/MultiplayerClient.cs

@@ -69,6 +69,11 @@ namespace osu.Game.Online.Multiplayer
         /// </summary>
         public virtual event Action? LoadRequested;
 
+        /// <summary>
+        /// Invoked when the multiplayer server requests loading of play to be aborted.
+        /// </summary>
+        public event Action? LoadAborted;
+
         /// <summary>
         /// Invoked when the multiplayer server requests gameplay to be started.
         /// </summary>
@@ -604,6 +609,19 @@ namespace osu.Game.Online.Multiplayer
             return Task.CompletedTask;
         }
 
+        Task IMultiplayerClient.LoadAborted()
+        {
+            Scheduler.Add(() =>
+            {
+                if (Room == null)
+                    return;
+
+                LoadAborted?.Invoke();
+            }, false);
+
+            return Task.CompletedTask;
+        }
+
         Task IMultiplayerClient.GameplayStarted()
         {
             Scheduler.Add(() =>

osu.Game/Online/Multiplayer/OnlineMultiplayerClient.cs

@@ -55,6 +55,7 @@ namespace osu.Game.Online.Multiplayer
                     connection.On<int, MultiplayerUserState>(nameof(IMultiplayerClient.UserStateChanged), ((IMultiplayerClient)this).UserStateChanged);
                     connection.On(nameof(IMultiplayerClient.LoadRequested), ((IMultiplayerClient)this).LoadRequested);
                     connection.On(nameof(IMultiplayerClient.GameplayStarted), ((IMultiplayerClient)this).GameplayStarted);
+                    connection.On(nameof(IMultiplayerClient.LoadAborted), ((IMultiplayerClient)this).LoadAborted);
                     connection.On(nameof(IMultiplayerClient.ResultsReady), ((IMultiplayerClient)this).ResultsReady);
                     connection.On<int, IEnumerable<APIMod>>(nameof(IMultiplayerClient.UserModsChanged), ((IMultiplayerClient)this).UserModsChanged);
                     connection.On<int, BeatmapAvailability>(nameof(IMultiplayerClient.UserBeatmapAvailabilityChanged), ((IMultiplayerClient)this).UserBeatmapAvailabilityChanged);