port polymer data binding tests

pkg/polymer/lib/src/instance.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of polymer;
 
 /**
  * Use this annotation to publish a field as an attribute. For example:
  *
  *     class MyPlaybackElement extends PolymerElement {
@@ skipping 491 matching lines @@
       _elementObservers = new Map<String, StreamSubscription>();
     }
     _elementObservers[name] = sub;
   }
 
   void observeAttributeProperty(String name) {
     _observe(name, (value, old) => reflectPropertyToAttribute(name));
   }
 
   void observeProperty(String name, Symbol method) {
-    final self = reflect(this);
-    _observe(name, (value, old) => self.invoke(method, [old]));
+    _observe(name, (value, old) => _invoke(method, [old]));
   }
 
   void observeBoth(String name, Symbol methodName) {
-    final self = reflect(this);
     _observe(name, (value, old) {
       reflectPropertyToAttribute(name);
-      self.invoke(methodName, [old]);
+      _invoke(methodName, [old]);
     });
   }
 
   void unbindProperty(String name) {
     if (_elementObservers == null) return;
     var sub = _elementObservers.remove(name);
     if (sub != null) sub.cancel();
   }
 
   void unbindAllProperties() {
@@ skipping 108 matching lines @@
 
   String findEventDelegate(Event event) =>
       _declaration._eventDelegates[_eventNameFromType(event.type)];
 
   /** Call [methodName] method on [this] with [args], if the method exists. */
   // TODO(jmesserly): I removed the [node] argument as it was unused. Reconcile.
   void dispatchMethod(Symbol methodName, List args) {
     bool log = _eventsLog.isLoggable(Level.INFO);
     if (log) _eventsLog.info('>>> [$localName]: dispatch $methodName');
 
-    // TODO(sigmund): consider making event listeners list all arguments
-    // explicitly. Unless VM mirrors are optimized first, this reflectClass call
-    // will be expensive once custom elements extend directly from Element (see
-    // dartbug.com/11108).
+    _invoke(methodName, args);
+
+    if (log) _eventsLog.info('<<< [$localName]: dispatch $methodName');
+
+    // TODO(jmesserly): workaround for HTML events not supporting zones.
+    performMicrotaskCheckpoint();
+  }
+
+  InstanceMirror _invoke(Symbol methodName, List args) {
+    // TODO(sigmund): consider making callbacks list all arguments
+    // explicitly. Unless VM mirrors are optimized first, this will be expensive
+    // once custom elements extend directly from Element (see issue 11108).
     var self = reflect(this);
     var method = self.type.methods[methodName];
     if (method != null) {
       // This will either truncate the argument list or extend it with extra
       // null arguments, so it will match the signature.
       // TODO(sigmund): consider accepting optional arguments when we can tell
       // them appart from named arguments (see http://dartbug.com/11334)
       args.length = method.parameters.where((p) => !p.isOptional).length;
     }
-    self.invoke(methodName, args);
-
-    if (log) _eventsLog.info('<<< [$localName]: dispatch $methodName');
-
-    // TODO(jmesserly): workaround for HTML events not supporting zones.
-    performMicrotaskCheckpoint();
+    return self.invoke(methodName, args);
   }
 
   void instanceEventListener(Event event) {
     _listenLocal(host, event);
   }
 
   // TODO(sjmiles): much of the below privatized only because of the vague
   // notion this code is too fiddly and we need to revisit the core feature
   void _listenLocal(Element host, Event event) {
     // TODO(jmesserly): do we need this check? It was using cancelBubble, see:
@@ skipping 243 matching lines @@
 }
 
 final Logger _observeLog = new Logger('polymer.observe');
 final Logger _eventsLog = new Logger('polymer.events');
 final Logger _unbindLog = new Logger('polymer.unbind');
 final Logger _bindLog = new Logger('polymer.bind');
 
 final Expando _shadowHost = new Expando<Element>();
 
 final Expando _eventHandledTable = new Expando<Set<Node>>();