Kill onDidMount()/onDidUnmount() in favour of just overriding the relevant methods.

sky/sdk/lib/framework/fn2.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 library fn;
 
 import 'app.dart';
 import 'dart:async';
 import 'dart:collection';
 import 'dart:mirrors';
@@ skipping 52 matching lines @@
       }
     }
   }
 
   static void _notifyMountStatusChanged() {
     try {
       _notifyingMountStatus = true;
       for (UINode node in _mountedChanged) {
         if (node._wasMounted != node._mounted) {
           if (node._mounted)
-            node._didMount();
+            node.didMount();
           else
-            node._didUnmount();
+            node.didUnmount();
           node._wasMounted = node._mounted;
         }
       }
       _mountedChanged.clear();
     } finally {
       _notifyingMountStatus = false;
     }
   }
-  void _didMount() { }
-  void _didUnmount() { }
+  void didMount() { }
+  void didUnmount() { }
 
   RenderObject root;
 
   // Subclasses which implements Nodes that become stateful may return true
   // if the |old| node has become stateful and should be retained.
   // This is called immediately before _sync().
   // Component._retainStatefulNodeIfPossible() calls syncFields().
   bool _retainStatefulNodeIfPossible(UINode old) => false;
 
   bool get interchangeable => false; // if true, then keys can be duplicated
@@ skipping 783 matching lines @@
   static Component _currentlyBuilding;
   bool get _isBuilding => _currentlyBuilding == this;
 
   bool _stateful;
   bool _dirty = true;
   bool _disqualifiedFromEverAppearingAgain = false;
 
   UINode _built;
   dynamic _slot; // cached slot from the last time we were synced
 
-  List<Function> _mountCallbacks;
-  List<Function> _unmountCallbacks;
-
-  void onDidMount(Function fn) {
-    if (_mountCallbacks == null)
-      _mountCallbacks = new List<Function>();
-
-    _mountCallbacks.add(fn);
-  }
-
-  void onDidUnmount(Function fn) {
-    if (_unmountCallbacks == null)
-      _unmountCallbacks = new List<Function>();
-
-    _unmountCallbacks.add(fn);
-  }
-
-  void _didMount() {
+  void didMount() {
     assert(!_disqualifiedFromEverAppearingAgain);
-    super._didMount();
-    if (_mountCallbacks != null)
-      for (Function fn in _mountCallbacks)
-        fn();
-  }
-
-  void _didUnmount() {
-    super._didUnmount();
-    if (_unmountCallbacks != null)
-      for (Function fn in _unmountCallbacks)
-        fn();
+    super.didMount();
   }
 
   void remove() {
     assert(_built != null);
     assert(root != null);
     removeChild(_built);
     _built = null;
     super.remove();
   }
 
@@ skipping 193 matching lines @@
   }
 
 }
 
 class Text extends Component {
   Text(this.data) : super(key: '*text*');
   final String data;
   bool get interchangeable => true;
   UINode build() => new Paragraph(text: data);
 }