Use a shared function to represent type substitutions with dynamic.

pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.new_js_emitter.emitter;
 
 import '../model.dart';
 import 'model_emitter.dart';
 import '../../common.dart';
 import '../../elements/elements.dart' show FieldElement;
@@ skipping 55 matching lines @@
     // name) which is unique.
     return namer.constantName(a).compareTo(namer.constantName(b));
   }
 
   @override
   js.Expression generateEmbeddedGlobalAccess(String global) {
     return _emitter.generateEmbeddedGlobalAccess(global);
   }
 
   @override
+  // TODO(herhut): Use a single shared function.
+  js.Expression generateFunctionThatReturnsNull() {
+    return js.js(r"""function() { return null; }""");

[floitsch, 2015/01/16 16:56:13]

Could we make this return `undefined` ?
Would make the function smaller...

No need for triple quotes.

+  }
+
+  @override
   js.Expression constantReference(ConstantValue value) {
     return _emitter.constantEmitter.reference(value);
   }
 
   js.PropertyAccess _globalPropertyAccess(Element element) {
      String name = namer.getNameX(element);
      js.PropertyAccess pa = new js.PropertyAccess.field(
          new js.VariableUse(namer.globalObjectFor(element)),
          name);
      return pa;
@@ skipping 43 matching lines @@
   @override
   js.Expression typeAccess(Element element) {
     // TODO(floitsch): minify 'ensureResolved'.
     // TODO(floitsch): don't emit `ensureResolved` for eager classes.
     return js.js('#.ensureResolved()', _globalPropertyAccess(element));
   }
 
   @override
   void invalidateCaches() {}
 }