Allow infering of return types on runtime helpers. It's only arugments the inferrer does not see.

sdk/lib/_internal/compiler/implementation/js_backend/backend.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 js_backend;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked;
 
   JavaScriptItemCompilationContext()
@@ skipping 885 matching lines @@
     enqueueInResolution(helper.getElement(compiler), elements);
     // We also need the native variant of the check (for DOM types).
     helper = getNativeCheckedModeHelper(type, typeCast: true);
     if (helper != null) {
       enqueueInResolution(helper.getElement(compiler), elements);
     }
   }
 
   void registerThrowNoSuchMethod(TreeElements elements) {
     enqueueInResolution(getThrowNoSuchMethod(), elements);
+    compiler.enqueuer.resolution.registerInstantiatedClass(

[ahe, 2013/08/15 11:27:43]

Please document that these represent the arguments passed to this method.

[ngeoffray, 2013/08/15 11:31:34]

Done.

+        compiler.listClass, elements);
+    enqueuer.registerInstantiatedClass(compiler.stringClass, elements);
   }
 
   void registerThrowRuntimeError(TreeElements elements) {
+    enqueuer.registerInstantiatedClass(compiler.stringClass, elements);

[ahe, 2013/08/15 11:27:43]

Ditto.

[ngeoffray, 2013/08/15 11:31:34]

Done.

     enqueueInResolution(getThrowRuntimeError(), elements);
   }
 
   void registerAbstractClassInstantiation(TreeElements elements) {
+    enqueuer.registerInstantiatedClass(compiler.stringClass, elements);

[ahe, 2013/08/15 11:27:43]

Ditto.

[ngeoffray, 2013/08/15 11:31:34]

Done.

     enqueueInResolution(getThrowAbstractClassInstantiationError(), elements);
   }
 
   void registerFallThroughError(TreeElements elements) {
     enqueueInResolution(getFallThroughError(), elements);
   }
 
   void registerSuperNoSuchMethod(TreeElements elements) {
     enqueueInResolution(getCreateInvocationMirror(), elements);
     enqueueInResolution(
@@ skipping 660 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }