dart2js send stats, includes:

pkg/compiler/lib/src/world.dart

 // Copyright (c) 2012, 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 dart2js;
 
 abstract class ClassWorld {
   // TODO(johnniwinther): Refine this into a `BackendClasses` interface.
   Backend get backend;
 
@@ skipping 347 matching lines @@
   void populate() {
     void addSubtypes(ClassElement cls) {
       if (compiler.hasIncrementalSupport && !alreadyPopulated.add(cls)) {
         return;
       }
       assert(cls.isDeclaration);
       if (!cls.isResolved) {
         compiler.internalError(cls, 'Class "${cls.name}" is not resolved.');
       }
 
+      // TODO(sigmund): split into separate CL. See dartbug.com/23664

[Johnni Winther, 2015/07/13 19:21:44]

Ahh, yes, the bug and its fix.

[Siggi Cherem (dart-lang), 2015/09/29 01:39:34]

:)

+      _subtypes.putIfAbsent(cls, () => new Set<ClassElement>()).add(cls);
+      _subclasses.putIfAbsent(cls, () => new Set<ClassElement>()).add(cls);
       for (DartType type in cls.allSupertypes) {
         Set<Element> subtypesOfSupertype =
             _subtypes.putIfAbsent(type.element, () => new Set<ClassElement>());
         subtypesOfSupertype.add(cls);
       }
 
       // Walk through the superclasses, and record the types
       // implemented by that type on the superclasses.
       ClassElement superclass = cls.superclass;
       while (superclass != null) {
@@ skipping 158 matching lines @@
     // function expressions's element.
     // TODO(herhut): Generate classes for function expressions earlier.
     if (element is closureMapping.SynthesizedCallMethodElementX) {
       return getMightBePassedToApply(element.expression);
     }
     return functionsThatMightBePassedToApply.contains(element);
   }
 
   bool get hasClosedWorldAssumption => !compiler.hasIncrementalSupport;
 }