Update signature of TryCreateServiceSessionAsync so an optional argument is clear

src/EditorFeatures/TestUtilities/Remote/InProcRemostHostClient.cs

@@ -59,7 +59,7 @@ public static async Task<RemoteHostClient> CreateAsync(Workspace workspace, bool
 
         public AssetStorage AssetStorage => _inprocServices.AssetStorage;
 
-        protected override async Task<Session> TryCreateServiceSessionAsync(string serviceName, Func<CancellationToken, Task<PinnedRemotableDataScope>> getSnapshotAsync, object callbackTarget, CancellationToken cancellationToken)
+        protected override async Task<Session> TryCreateServiceSessionAsync(string serviceName, Optional<Func<CancellationToken, Task<PinnedRemotableDataScope>>> getSnapshotAsync, object callbackTarget, CancellationToken cancellationToken)
         {
             // get stream from service hub to communicate snapshot/asset related information
             // this is the back channel the system uses to move data between VS and remote host

src/VisualStudio/Core/Next/Remote/JsonRpcSession.cs

@@ -31,13 +31,13 @@ internal class JsonRpcSession : RemoteHostClient.Session
         private readonly CancellationTokenRegistration _cancellationRegistration;
 
         public static async Task<JsonRpcSession> CreateAsync(
-            Func<CancellationToken, Task<PinnedRemotableDataScope>> getSnapshotAsync,
+            Optional<Func<CancellationToken, Task<PinnedRemotableDataScope>>> getSnapshotAsync,
             object callbackTarget,
             Stream serviceStream,
             Stream snapshotStreamOpt,
             CancellationToken cancellationToken)
         {
-            var snapshot = getSnapshotAsync == null ? null : await getSnapshotAsync(cancellationToken).ConfigureAwait(false);
+            var snapshot = getSnapshotAsync.Value == null ? null : await getSnapshotAsync.Value(cancellationToken).ConfigureAwait(false);
 
             JsonRpcSession session;
             try

src/VisualStudio/Core/Next/Remote/ServiceHubRemoteHostClient.cs

@@ -5,6 +5,7 @@
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.ErrorReporting;
 using Microsoft.CodeAnalysis.Execution;
@@ -114,11 +115,11 @@ private static async Task RegisterWorkspaceHostAsync(Workspace workspace, Remote
             _rpc.StartListening();
         }
 
-        protected override async Task<Session> TryCreateServiceSessionAsync(string serviceName, Func<CancellationToken, Task<PinnedRemotableDataScope>> getSnapshotAsync, object callbackTarget, CancellationToken cancellationToken)
+        protected override async Task<Session> TryCreateServiceSessionAsync(string serviceName, Optional<Func<CancellationToken, Task<PinnedRemotableDataScope>>> getSnapshotAsync, object callbackTarget, CancellationToken cancellationToken)
         {
             // get stream from service hub to communicate snapshot/asset related information
             // this is the back channel the system uses to move data between VS and remote host for solution related information
-            var snapshotStream = getSnapshotAsync == null ? null : await RequestServiceAsync(_hubClient, WellKnownServiceHubServices.SnapshotService, _hostGroup, _timeout, cancellationToken).ConfigureAwait(false);
+            var snapshotStream = getSnapshotAsync.Value != null ? null : await RequestServiceAsync(_hubClient, WellKnownServiceHubServices.SnapshotService, _hostGroup, _timeout, cancellationToken).ConfigureAwait(false);
 
             // get stream from service hub to communicate service specific information
             // this is what consumer actually use to communicate information

src/Workspaces/Core/Portable/Remote/RemoteHostClient.cs

@@ -77,7 +77,7 @@ public async Task<Session> TryCreateServiceSessionAsync(string serviceName, Solu
 
         protected abstract void OnDisconnected();
 
-        protected abstract Task<Session> TryCreateServiceSessionAsync(string serviceName, Func<CancellationToken, Task<PinnedRemotableDataScope>> getSnapshotAsync, object callbackTarget, CancellationToken cancellationToken);
+        protected abstract Task<Session> TryCreateServiceSessionAsync(string serviceName, Optional<Func<CancellationToken, Task<PinnedRemotableDataScope>>> getSnapshotAsync, object callbackTarget, CancellationToken cancellationToken);
 
         internal void Shutdown()
         {
@@ -175,7 +175,7 @@ public class NoOpClient : RemoteHostClient
             }
 
             protected override Task<Session> TryCreateServiceSessionAsync(
-                string serviceName, Func<CancellationToken, Task<PinnedRemotableDataScope>> getSnapshotAsync, object callbackTarget, CancellationToken cancellationToken)
+                string serviceName, Optional<Func<CancellationToken, Task<PinnedRemotableDataScope>>> getSnapshotAsync, object callbackTarget, CancellationToken cancellationToken)
             {
                 return SpecializedTasks.Default<Session>();
             }