perf(view factory): 14% Precompute linking information for nodes

The Default TreeComponent benchmark dropped from 572ms to 501ms

Closes #1194
Closes #1196

lib/core_dom/tagging_view_factory.dart

@@ -1,11 +1,55 @@
 part of angular.core.dom_internal;
 
+class NodeLinkingInfo {
+  /**
+   * True if the Node has a 'ng-binding' class.
+   */
+  final bool containsNgBinding;
+
+  /**
+   * True if the Node is a [dom.Element], otherwise it is a Text or Comment node.
+   * No other nodeTypes are allowed.
+   */
+  final bool isElement;
+
+  /**
+   * If true, some child has a 'ng-binding' class and the ViewFactory must search
+   * for these children.
+   */
+  final bool ngBindingChildren;
+
+  NodeLinkingInfo(this.containsNgBinding, this.isElement, this.ngBindingChildren);
+}
+
+computeNodeLinkingInfos(List<dom.Node> nodeList) {
+  List<NodeLinkingInfo> list = new List<NodeLinkingInfo>(nodeList.length);
+
+  for (int i = 0; i < nodeList.length; i++) {
+    dom.Node node = nodeList[i];
+
+    assert(node.nodeType == dom.Node.ELEMENT_NODE ||
+           node.nodeType == dom.Node.TEXT_NODE ||
+           node.nodeType == dom.Node.COMMENT_NODE);
+
+    bool isElement = node.nodeType == dom.Node.ELEMENT_NODE;
+
+    list[i] = new NodeLinkingInfo(
+        isElement && (node as dom.Element).classes.contains('ng-binding'),
+        isElement,
+        isElement && (node as dom.Element).querySelectorAll('.ng-binding').length > 0);
+  }
+  return list;
+}
+
 class TaggingViewFactory implements ViewFactory {
   final List<TaggedElementBinder> elementBinders;
   final List<dom.Node> templateNodes;
+  final List<NodeLinkingInfo> nodeLinkingInfos;
   final Profiler _perf;
 
-  TaggingViewFactory(this.templateNodes, this.elementBinders, this._perf);
+  TaggingViewFactory(templateNodes, this.elementBinders, this._perf) :
+      nodeLinkingInfos = computeNodeLinkingInfos(templateNodes),
+      this.templateNodes = templateNodes;
 
   BoundViewFactory bind(Injector injector) => new BoundViewFactory(this, injector);
 
@@ -51,7 +95,8 @@ class TaggingViewFactory implements ViewFactory {
 
     var elementBinderIndex = 0;
     for (int i = 0; i < nodeList.length; i++) {
-      var node = nodeList[i];
+      dom.Node node = nodeList[i];
+      NodeLinkingInfo linkingInfo = nodeLinkingInfos[i];
 
       // if node isn't attached to the DOM, create a parent for it.
       var parentNode = node.parentNode;
@@ -62,29 +107,27 @@ class TaggingViewFactory implements ViewFactory {
         parentNode.append(node);
       }
 
-      if (node.nodeType == dom.Node.ELEMENT_NODE) {
-        var elts = node.querySelectorAll('.ng-binding');
-        // querySelectorAll doesn't return the node itself
-        if (node.classes.contains('ng-binding')) {
+      if (linkingInfo.isElement) {
+        if (linkingInfo.containsNgBinding) {
           var tagged = elementBinders[elementBinderIndex];
           _bindTagged(tagged, elementBinderIndex, rootInjector, elementInjectors, view, node);
           elementBinderIndex++;
         }
 
-        for (int j = 0; j < elts.length; j++, elementBinderIndex++) {
-          TaggedElementBinder tagged = elementBinders[elementBinderIndex];
-          _bindTagged(tagged, elementBinderIndex, rootInjector, elementInjectors, view, elts[j]);
+        if (linkingInfo.ngBindingChildren) {
+          var elts = (node as dom.Element).querySelectorAll('.ng-binding');
+          for (int j = 0; j < elts.length; j++, elementBinderIndex++) {
+            TaggedElementBinder tagged = elementBinders[elementBinderIndex];
+            _bindTagged(tagged, elementBinderIndex, rootInjector, elementInjectors, view, elts[j]);
+          }
         }
-      } else if (node.nodeType == dom.Node.TEXT_NODE ||
-                 node.nodeType == dom.Node.COMMENT_NODE) {
+      } else {
         TaggedElementBinder tagged = elementBinders[elementBinderIndex];
         assert(tagged.binder != null || tagged.isTopLevel);
         if (tagged.binder != null) {
           _bindTagged(tagged, elementBinderIndex, rootInjector, elementInjectors, view, node);
         }
         elementBinderIndex++;
-      } else {
-        throw "nodeType sadness ${node.nodeType}}";
       }
 
       if (fakeParent) {