Add ability for callback to specify a message to display to the user.

src/EditorFeatures/Core/FindUsages/FindUsagesContext.cs

@@ -14,6 +14,10 @@ protected FindUsagesContext()
         {
         }
 
+        public virtual void ReportMessage(string message)
+        {
+        }
+
         public virtual void SetSearchLabel(string displayName)
         {
         }

src/EditorFeatures/Core/FindUsages/IFindUsagesContext.cs

@@ -9,6 +9,14 @@ internal interface IFindUsagesContext
     {
         CancellationToken CancellationToken { get; }
 
+        /// <summary>
+        /// Report a message to be displayed to the user.
+        /// </summary>
+        void ReportMessage(string message);
+
+        /// <summary>
+        /// Set the title of the window that results are displayed in.
+        /// </summary>
         void SetSearchLabel(string displayName);
 
         Task OnDefinitionFoundAsync(DefinitionItem definition);