Delete the ability to asynchronously get the PrimaryWorkspace

Nobody was using this.

src/Workspaces/Core/Portable/Workspace/PrimaryWorkspace.cs

@@ -11,12 +11,8 @@ namespace Microsoft.CodeAnalysis
     internal static class PrimaryWorkspace
     {
         private static readonly ReaderWriterLockSlim s_registryGate = new ReaderWriterLockSlim(LockRecursionPolicy.NoRecursion);
-
         private static Workspace s_primaryWorkspace;
 
-        private static readonly List<TaskCompletionSource<Workspace>> s_primaryWorkspaceTaskSourceList =
-            new List<TaskCompletionSource<Workspace>>();
-
         /// <summary>
         /// The primary workspace, usually set by the host environment.
         /// </summary>
@@ -44,56 +40,6 @@ public static void Register(Workspace workspace)
             using (s_registryGate.DisposableWrite())
             {
                 s_primaryWorkspace = workspace;
-
-                foreach (var taskSource in s_primaryWorkspaceTaskSourceList)
-                {
-                    try
-                    {
-                        taskSource.TrySetResult(workspace);
-                    }
-                    catch
-                    {
-                    }
-                }
-
-                s_primaryWorkspaceTaskSourceList.Clear();
-            }
-        }
-
-        /// <summary>
-        /// Get's the primary workspace asynchronously.
-        /// </summary>
-        public static Task<Workspace> GetWorkspaceAsync(CancellationToken cancellationToken = default(CancellationToken))
-        {
-            using (s_registryGate.DisposableWrite())
-            {
-                if (s_primaryWorkspace != null)
-                {
-                    return Task<Workspace>.FromResult(s_primaryWorkspace);
-                }
-                else
-                {
-                    var taskSource = new TaskCompletionSource<Workspace>();
-
-                    if (cancellationToken.CanBeCanceled)
-                    {
-                        try
-                        {
-                            var registration = cancellationToken.Register(() =>
-                            {
-                                taskSource.TrySetCanceled();
-                            });
-
-                            taskSource.Task.ContinueWith(_ => registration.Dispose(), CancellationToken.None, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Default);
-                        }
-                        catch
-                        {
-                        }
-                    }
-
-                    s_primaryWorkspaceTaskSourceList.Add(taskSource);
-                    return taskSource.Task;
-                }
             }
         }
     }