dart2js send stats, includes:

pkg/compiler/lib/src/resolution/tree_elements.dart

 // Copyright (c) 2015, 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 resolution;
 
 abstract class TreeElements {
   AnalyzableElement get analyzedElement;
   Iterable<Node> get superUses;
 
   /// Iterables of the dependencies that this [TreeElement] records of
   /// [analyzedElement].
   Iterable<Element> get allElements;
   void forEachConstantNode(f(Node n, ConstantExpression c));
 
   /// A set of additional dependencies.  See [registerDependency] below.
   Iterable<Element> get otherDependencies;
 
   Element operator[](Node node);
+  Map<Node, DartType> get typesCache;
 
   SendStructure getSendStructure(Send send);
 
   // TODO(johnniwinther): Investigate whether [Node] could be a [Send].
   Selector getSelector(Node node);
   Selector getGetterSelectorInComplexSendSet(SendSet node);
   Selector getOperatorSelectorInComplexSendSet(SendSet node);
   DartType getType(Node node);
   TypeMask getTypeMask(Node node);
   TypeMask getGetterTypeMaskInComplexSendSet(SendSet node);
@@ skipping 63 matching lines @@
 
   /// Returns the label that [node] targets.
   LabelDefinition getTargetLabel(GotoStatement node);
 }
 
 class TreeElementMapping extends TreeElements {
   final AnalyzableElement analyzedElement;
   Map<Spannable, Selector> _selectors;
   Map<Spannable, TypeMask> _typeMasks;
   Map<Node, DartType> _types;
+  Map<Node, DartType> typesCache = <Node, DartType>{};
   Setlet<Node> _superUses;
   Setlet<Element> _otherDependencies;
   Map<Node, ConstantExpression> _constants;
   Map<VariableElement, List<Node>> _potentiallyMutated;
   Map<Node, Map<VariableElement, List<Node>>> _potentiallyMutatedIn;
   Map<VariableElement, List<Node>> _potentiallyMutatedInClosure;
   Map<Node, Map<VariableElement, List<Node>>> _accessedByClosureIn;
   Setlet<Element> _elements;
   Setlet<Send> _asserts;
   Maplet<Send, SendStructure> _sendStructureMap;
@@ skipping 413 matching lines @@
   TreeElements get treeElements {
     assert(invariant(this, _treeElements !=null,
         message: "TreeElements have not been computed for $this."));
     return _treeElements;
   }
 
   void reuseElement() {
     _treeElements = null;
   }
 }