dart2js: register output units explicitly in the program builder.

pkg/compiler/lib/src/js_emitter/program_builder.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.js_emitter.program_builder;
 
 import 'js_emitter.dart' show computeMixinClass;
 import 'model.dart';
 
 import '../common.dart';
@@ skipping 40 matching lines @@
 
   /// Mapping from [OutputUnit] to constructed [Fragment]. We need this to
   /// generate the deferredLoadingMap (to know which hunks to load).
   final Map<OutputUnit, Fragment> _outputs = <OutputUnit, Fragment>{};
 
   /// Mapping from [ConstantValue] to constructed [Constant]. We need this to
   /// update field-initializers to point to the ConstantModel.
   final Map<ConstantValue, Constant> _constants = <ConstantValue, Constant>{};
 
   Program buildProgram() {
+    // Note: In rare cases (mostly tests) output units can be empty. This
+    // happens when the deferred code is dead-code eliminated but we still need
+    // to check that the library has been loaded.
+    _compiler.deferredLoadTask.allOutputUnits.forEach(
+        _registry.registerOutputUnit);
     _task.outputClassLists.forEach(_registry.registerElements);
     _task.outputStaticLists.forEach(_registry.registerElements);
     _task.outputConstantLists.forEach(_registerConstants);
 
     // TODO(kasperl): There's code that implicitly needs access to the special
     // $ holder so we have to register that. Can we track if we have to?
     _registry.registerHolder(r'$');
 
     MainFragment mainOutput = _buildMainOutput(_registry.mainLibrariesMap);
     Iterable<Fragment> deferredOutputs = _registry.deferredLibrariesMap
@@ skipping 372 matching lines @@
       _registry.registerConstant(outputUnit, constantValue);
       assert(!_constants.containsKey(constantValue));
       String name = namer.constantName(constantValue);
       String constantObject = namer.globalObjectForConstant(constantValue);
       Holder holder = _registry.registerHolder(constantObject);
       Constant constant = new Constant(name, holder, constantValue);
       _constants[constantValue] = constant;
     };
   }
 }