Fix unit tests.

src/AddIns/DisplayBindings/XmlEditor/Test/Utils/MockTextEditor.cs

@@ -179,7 +179,7 @@ namespace XmlEditor.Tests.Utils
 		
 		public object GetService(Type serviceType)
 		{
-			throw new NotImplementedException();
+			return document.GetService(serviceType);
 		}
 		
 		public IList<ICSharpCode.SharpDevelop.Refactoring.IContextActionProvider> ContextActionProviders {

src/AddIns/DisplayBindings/XmlEditor/Test/Utils/MockTextEditorProviderViewContent.cs

@@ -24,5 +24,10 @@ namespace XmlEditor.Tests.Utils
 		{
 			throw new NotImplementedException();
 		}
+		
+		public override object GetService(Type serviceType)
+		{
+			return textEditor.GetService(serviceType);
+		}
 	}
 }

src/AddIns/DisplayBindings/XmlEditor/Test/Utils/MockViewContent.cs

@@ -184,7 +184,7 @@ namespace XmlEditor.Tests.Utils
 			throw new NotImplementedException();
 		}
 		
-		public object GetService(Type serviceType)
+		public virtual object GetService(Type serviceType)
 		{
 			return null;
 		}