Call AdviseRunningDocTableEvents on UI thread take 2.

- Originally when this work was done I attempted to call the advise in the ctor; however, that in practice didn't work out so well. Therefore, given that the editor document manager is always "started" / requested elsewhere we can lazily advise the running document table when already on the UI thread.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1441597

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/Documents/VisualStudioEditorDocumentManager.cs

@@ -25,6 +25,7 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
 
         private readonly Dictionary<uint, List<DocumentKey>> _documentsByCookie;
         private readonly Dictionary<DocumentKey, uint> _cookiesByDocument;
+        private bool _advised;
 
         public VisualStudioEditorDocumentManager(
             ProjectSnapshotManagerDispatcher projectSnapshotManagerDispatcher,
@@ -52,9 +53,6 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
             _runningDocumentTable = (IVsRunningDocumentTable4)runningDocumentTable;
             _editorAdaptersFactory = editorAdaptersFactory;
 
-            var hr = runningDocumentTable.AdviseRunningDocTableEvents(new RunningDocumentTableEventSink(this), out _);
-            Marshal.ThrowExceptionForHR(hr);
-
             _documentsByCookie = new Dictionary<uint, List<DocumentKey>>();
             _cookiesByDocument = new Dictionary<DocumentKey, uint>();
         }
@@ -68,6 +66,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
 
             JoinableTaskContext.AssertUIThread();
 
+            EnsureDocumentTableAdvised();
+
             // Check if the document is already open and initialized, and associate a buffer if possible.
             uint cookie;
             if (_runningDocumentTable.IsMonikerValid(filePath) &&
@@ -90,6 +90,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         {
             JoinableTaskContext.AssertUIThread();
 
+            EnsureDocumentTableAdvised();
+
             var cookie = _runningDocumentTable.GetDocumentCookie(document.DocumentFilePath);
             if (cookie != VSConstants.VSCOOKIE_NIL)
             {
@@ -101,6 +103,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         {
             JoinableTaskContext.AssertUIThread();
 
+            EnsureDocumentTableAdvised();
+
             var key = new DocumentKey(document.ProjectFilePath, document.DocumentFilePath);
             if (_cookiesByDocument.TryGetValue(key, out var cookie))
             {
@@ -112,6 +116,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         {
             JoinableTaskContext.AssertUIThread();
 
+            EnsureDocumentTableAdvised();
+
             lock (Lock)
             {
                 // Casts avoid dynamic
@@ -148,6 +154,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         {
             JoinableTaskContext.AssertUIThread();
 
+            EnsureDocumentTableAdvised();
+
             var textBuffer = _editorAdaptersFactory.GetDocumentBuffer(vsTextBuffer);
             if (textBuffer != null)
             {
@@ -164,6 +172,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         {
             JoinableTaskContext.AssertUIThread();
 
+            EnsureDocumentTableAdvised();
+
             lock (Lock)
             {
                 for (var i = 0; i < documents.Length; i++)
@@ -177,6 +187,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         {
             JoinableTaskContext.AssertUIThread();
 
+            EnsureDocumentTableAdvised();
+
             lock (Lock)
             {
                 if (!_documentsByCookie.TryGetValue(cookie, out var documents))
@@ -201,6 +213,8 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
         {
             JoinableTaskContext.AssertUIThread();
 
+            EnsureDocumentTableAdvised();
+
             // Ignore changes is casing
             if (FilePathComparer.Instance.Equals(fromFilePath, toFilePath))
             {
@@ -223,6 +237,18 @@ namespace Microsoft.VisualStudio.Editor.Razor.Documents
             }
         }
 
+        private void EnsureDocumentTableAdvised()
+        {
+            JoinableTaskContext.AssertUIThread();
+
+            if (!_advised)
+            {
+                _advised = true;
+                var hr = ((IVsRunningDocumentTable)_runningDocumentTable).AdviseRunningDocTableEvents(new RunningDocumentTableEventSink(this), out _);
+                Marshal.ThrowExceptionForHR(hr);
+            }
+        }
+
         private void TrackOpenDocument(uint cookie, DocumentKey key)
         {
             if (!_documentsByCookie.TryGetValue(cookie, out var documents))