Add back didMount

sky/framework/fn.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 'dart:async';
 import 'dart:collection';
 import 'dart:sky' as sky;
 import 'reflect.dart' as reflect;
@@ skipping 532 matching lines @@
   final int _order;
   static int _currentOrder = 0;
   bool _stateful;
   static Component _currentlyRendering;
 
   Component({ Object key, bool stateful })
       : _stateful = stateful != null ? stateful : false,
         _order = _currentOrder + 1,
         super(key:key);
 
+  void didMount() {}
   void didUnmount() {}
 
   void _remove() {
     assert(_rendered != null);
     assert(_root != null);
     _rendered._remove();
     _rendered = null;
     _root = null;
     _removed = true;
     didUnmount();
@@ skipping 32 matching lines @@
     return false;
   }
 
   void _renderInternal(sky.Node host, sky.Node insertBefore) {
     if (!_dirty) {
       assert(_rendered != null);
       return;
     }
 
     var oldRendered = _rendered;
+    bool mounting = oldRendered == null;
     int lastOrder = _currentOrder;
     _currentOrder = _order;
     _currentlyRendering = this;
     _rendered = render();
     _currentlyRendering = null;
     _currentOrder = lastOrder;
 
     _rendered.events.addAll(events);
 
     _dirty = false;
 
     if (oldRendered != null && _rendered.runtimeType != oldRendered.runtimeType)
       oldRendered = null;
 
     if (_rendered._sync(oldRendered, host, insertBefore)) {
       _rendered = oldRendered; // retain stateful component
     }
     _root = _rendered._root;
     assert(_rendered._root is sky.Node);
+
+    if (mounting) {
+      didMount();
+    }
   }
 
   void _renderIfDirty() {
     assert(_rendered != null);
     assert(!_removed);
 
     var rendered = _rendered;
     while (rendered is Component) {
       rendered = rendered._rendered;
     }
@@ skipping 26 matching lines @@
 
       _sync(null, _host, null);
       assert(_root is sky.Node);
 
       sw.stop();
       if (_shouldLogRenderDuration)
         print("Initial render: ${sw.elapsedMicroseconds} microseconds");
     });
   }
 }