dart2js: Support mock compilation in the program builder.

pkg/compiler/lib/src/js_emitter/program_builder/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, Emitter;
 import '../model.dart';
 
 import '../../common.dart';
@@ skipping 190 matching lines @@
         _buildInvokeMain(),
         _buildLibraries(librariesMap),
         _buildStaticNonFinalFields(librariesMap),
         _buildStaticLazilyInitializedFields(librariesMap),
         _buildConstants(librariesMap));
     _outputs[librariesMap.outputUnit] = result;
     return result;
   }
 
   js.Statement _buildInvokeMain() {
+    if (_compiler.isMockCompilation) return js.js.comment("Mock compilation");
+
     MainCallStubGenerator generator =
         new MainCallStubGenerator(_compiler, backend, backend.emitter);
     return generator.generateInvokeMain();
   }
 
   DeferredFragment _buildDeferredFragment(LibrariesMap librariesMap) {
     DeferredFragment result = new DeferredFragment(
         librariesMap.outputUnit,
         backend.deferredPartFileName(librariesMap.name, addExtension: false),
                                      librariesMap.name,
@@ skipping 569 matching lines @@
       _registry.registerConstant(outputUnit, constantValue);
       assert(!_constants.containsKey(constantValue));
       js.Name name = namer.constantName(constantValue);
       String constantObject = namer.globalObjectForConstant(constantValue);
       Holder holder = _registry.registerHolder(constantObject);
       Constant constant = new Constant(name, holder, constantValue);
       _constants[constantValue] = constant;
     }
   }
 }