Fix for the js-interop crash

tests/compiler/dart2js/compiler_helper.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.
 
 library compiler_helper;
 
 import 'dart:async';
 import "package:expect/expect.dart";
 
 import 'package:compiler/src/elements/elements.dart'
@@ skipping 25 matching lines @@
 export 'package:compiler/src/tree/tree.dart';
 
 import 'mock_compiler.dart';
 export 'mock_compiler.dart';
 
 import 'memory_compiler.dart' hide compilerFor;
 
 import 'output_collector.dart';
 export 'output_collector.dart';
 
-/// Compile [code] and returns the code for [entry].
+/// Compile [code] and returns either the code for [entry] or, if [returnAll] is
+/// true, the code for the entire program.
 ///
 /// If [check] is provided, it is executed on the code for [entry] before
 /// returning. If [useMock] is `true` the [MockCompiler] is used for
 /// compilation, otherwise the memory compiler is used.
 Future<String> compile(String code,
                        {String entry: 'main',
                         bool enableTypeAssertions: false,
                         bool minify: false,
                         bool analyzeAll: false,
                         bool disableInlining: true,
                         bool useMock: false,
-                        void check(String generated)}) async {
+                        void check(String generatedEntry),
+                        bool returnAll: false}) async {
+  OuputCollector outputCollector = returnAll ? new OutputCollector() : null;
   if (useMock) {
     // TODO(johnniwinther): Remove this when no longer needed by
     // `arithmetic_simplication_test.dart`.
     MockCompiler compiler = new MockCompiler.internal(
         enableTypeAssertions: enableTypeAssertions,
         // Type inference does not run when manually
         // compiling a method.
         disableTypeInference: true,
         enableMinification: minify,
-        disableInlining: disableInlining);
+        disableInlining: disableInlining,
+        outputProvider: outputCollector);
     await compiler.init();
     compiler.parseScript(code);
     lego.Element element = compiler.mainApp.find(entry);
     if (element == null) return null;
     compiler.phase = Compiler.PHASE_RESOLVING;
     compiler.backend.enqueueHelpers(compiler.enqueuer.resolution,
                                     compiler.globalDependencies);
     compiler.processQueue(compiler.enqueuer.resolution, element);
     compiler.world.populate();
     compiler.backend.onResolutionComplete();
     var context = new js.JavaScriptItemCompilationContext();
     ResolutionWorkItem resolutionWork =
         new ResolutionWorkItem(element, context);
     resolutionWork.run(compiler, compiler.enqueuer.resolution);
     CodegenWorkItem work =
         new CodegenWorkItem(compiler, element, context);
     compiler.phase = Compiler.PHASE_COMPILING;
     work.run(compiler, compiler.enqueuer.codegen);
     js.JavaScriptBackend backend = compiler.backend;
     String generated = backend.getGeneratedCode(element);
     if (check != null) {
       check(generated);
     }
-    return generated;
+    return returnAll ? outputCollector.getOutput('', 'js') : generated;
   } else {
     List<String> options = <String>[
         Flags.disableTypeInference];
     if (enableTypeAssertions) {
       options.add(Flags.enableCheckedMode);
     }
     if (minify) {
       options.add(Flags.minify);
     }
     if (analyzeAll) {
       options.add(Flags.analyzeAll);
     }
 
     Map<String, String> source;
     if (entry != 'main') {
       source = {'main.dart': "$code\n\nmain() => $entry;" };
     } else {
       source = {'main.dart': code};
     }
 
     CompilationResult result = await runCompiler(
         memorySourceFiles: source,
         options: options,
+        outputProvider: outputCollector,
         beforeRun: (compiler) {
           if (disableInlining) {
             compiler.disableInlining = true;
           }
         });
     Expect.isTrue(result.isSuccess);
     Compiler compiler =  result.compiler;
     lego.Element element = compiler.mainApp.find(entry);
     js.JavaScriptBackend backend = compiler.backend;
     String generated = backend.getGeneratedCode(element);
     if (check != null) {
       check(generated);
     }
-    return generated;
+    return returnAll ? outputCollector.getOutput('', 'js') : generated;
   }
 }
 
 Future<String> compileAll(String code,
                           {Map<String, String> coreSource,
                            bool disableInlining: true,
                            bool trustTypeAnnotations: false,
                            bool minify: false,
                            int expectedErrors,
                            int expectedWarnings}) {
@@ skipping 141 matching lines @@
     regexp = regexp.replaceAll(xRe, '(?:$anyIdentifier)');
     final spaceRe = new RegExp('\\s+');
     regexp = regexp.replaceAll(spaceRe, '(?:\\s*)');
     if (shouldMatch) {
       Expect.isTrue(new RegExp(regexp).hasMatch(generated));
     } else {
       Expect.isFalse(new RegExp(regexp).hasMatch(generated));
     }
   });
 }