Speed up CompoundBindings

pkg/mdv/lib/src/template_iterator.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 mdv;
 
 // This code is a port of Model-Driven-Views:
 // https://github.com/polymer-project/mdv
 // The code mostly comes from src/template_element.js
 
@@ skipping 81 matching lines @@
     BindingDelegate delegate) {
 
   // If this is a custom element, give the .xtag a change to bind.
   node = _nodeOrCustom(node);
 
   if (_isSimpleBinding(tokens)) {
     _bindOrDelegate(node, name, model, tokens[1], delegate);
     return;
   }
 
-  var replacementBinding = new CompoundBinding();
-  for (var i = 1; i < tokens.length; i += 2) {
-    // TODO(jmesserly): not sure if this index is correct. See my comment here:
-    // https://github.com/Polymer/mdv/commit/f1af6fe683fd06eed2a7a7849f01c227db12cda3#L0L1035
-    _bindOrDelegate(replacementBinding, i, model, tokens[i], delegate);
-  }
-
-  replacementBinding.combinator = (values) {
+  // TODO(jmesserly): MDV caches the closure on the tokens, but I'm not sure
+  // why they do that instead of just caching the entire CompoundBinding object
+  // and unbindAll then bind to the new model.
+  var replacementBinding = new CompoundBinding()
+      ..scheduled = true
+      ..combinator = (values) {
     var newValue = new StringBuffer();
 
     for (var i = 0, text = true; i < tokens.length; i++, text = !text) {
       if (text) {
         newValue.write(tokens[i]);
       } else {
         var value = values[i];
         if (value != null) {
           newValue.write(value);
         }
       }
     }
 
     return newValue.toString();
   };
 
+  for (var i = 1; i < tokens.length; i += 2) {
+    // TODO(jmesserly): not sure if this index is correct. See my comment here:
+    // https://github.com/Polymer/mdv/commit/f1af6fe683fd06eed2a7a7849f01c227db12cda3#L0L1035
+    _bindOrDelegate(replacementBinding, i, model, tokens[i], delegate);
+  }
+
+  replacementBinding.resolve();
+
   node.bind(name, replacementBinding, 'value');
 }
 
 void _bindOrDelegate(node, name, model, String path,
     BindingDelegate delegate) {
 
   if (delegate != null) {
     var delegateBinding = delegate.getBinding(model, path, name, node);
     if (delegateBinding != null) {
       model = delegateBinding;
@@ skipping 265 matching lines @@
         nodeExt._templateIterator = null;
       }
     }
 
     _nodeOrCustom(node).unbindAll();
     for (var c = node.firstChild; c != null; c = c.nextNode) {
       _unbindAllRecursively(c);
     }
   }
 }