Make UserControl a name scope.

Closes #322.

src/Perspex.Controls/UserControl.cs

@@ -6,8 +6,42 @@ using Perspex.Styling;
 
 namespace Perspex.Controls
 {
-    public class UserControl : ContentControl, IStyleable
+    public class UserControl : ContentControl, IStyleable, INameScope
     {
+        private NameScope _nameScope = new NameScope();
+
+        /// <inheritdoc/>
+        event EventHandler<NameScopeEventArgs> INameScope.Registered
+        {
+            add { _nameScope.Registered += value; }
+            remove { _nameScope.Registered -= value; }
+        }
+
+        /// <inheritdoc/>
+        event EventHandler<NameScopeEventArgs> INameScope.Unregistered
+        {
+            add { _nameScope.Unregistered += value; }
+            remove { _nameScope.Unregistered -= value; }
+        }
+
         Type IStyleable.StyleKey => typeof(ContentControl);
+
+        /// <inheritdoc/>
+        void INameScope.Register(string name, object element)
+        {
+            _nameScope.Register(name, element);
+        }
+
+        /// <inheritdoc/>
+        object INameScope.Find(string name)
+        {
+            return _nameScope.Find(name);
+        }
+
+        /// <inheritdoc/>
+        void INameScope.Unregister(string name)
+        {
+            _nameScope.Unregister(name);
+        }
     }
 }