handle call hierarchy handler

src/VisualStudio/Core/Def/Implementation/CallHierarchy/CallHierarchyCommandHandler.cs

@@ -4,10 +4,10 @@
 using System.ComponentModel.Composition;
 using System.Linq;
 using Microsoft.CodeAnalysis.Editor.Host;
+using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
 using Microsoft.CodeAnalysis.FindSymbols;
 using Microsoft.CodeAnalysis.Notification;
 using Microsoft.CodeAnalysis.SymbolMapping;
-using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.Commanding;
 using Microsoft.VisualStudio.Text.Editor.Commanding.Commands;
 using Microsoft.VisualStudio.Utilities;
@@ -46,7 +46,8 @@ private void AddRootNode(ViewCallHierarchyCommandArgs args, CommandExecutionCont
             using (var waitScope = context.OperationContext.AddScope(allowCancellation: true, EditorFeaturesResources.Computing_Call_Hierarchy_Information))
             {
                 var cancellationToken = context.OperationContext.UserCancellationToken;
-                var document = args.SubjectBuffer.CurrentSnapshot.GetOpenDocumentInCurrentContextWithChanges();
+                var document = args.SubjectBuffer.CurrentSnapshot.GetFullyLoadedOpenDocumentInCurrentContextWithChangesAsync(
+                    context.OperationContext).WaitAndGetResult(cancellationToken);
                 if (document == null)
                 {
                     return;