Enable DDC output to run on v8/d8 using ES6 modules

pkg/dev_compiler/lib/src/compiler/module_builder.dart

 // Copyright (c) 2015, 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.
 
 import 'package:args/args.dart' show ArgParser, ArgResults;
 import 'package:path/path.dart' as path;
 
 import '../js_ast/js_ast.dart';
 import 'js_names.dart';
 
@@ skipping 194 matching lines @@
           "Imports", new ArrayInitializer(importNames, multiline: true)),
       resultModule
     ]);
     return new Program(<ModuleItem>[moduleDef]);
   }
 }
 
 /// Generates CommonJS modules (used by Node.js).
 class CommonJSModuleBuilder extends _ModuleBuilder {
   Program build(Program module) {
-    var importStatements = <Statement>[];
+    var importStatements = [js.statement("'use strict';"),];
 
     // Collect imports/exports/statements.
     visitProgram(module);
 
     for (var import in imports) {
       // TODO(jmesserly): we could use destructuring here.
       var moduleVar =
           new TemporaryId(pathToJSIdentifier(import.from.valueWithoutQuotes));
       importStatements
           .add(js.statement('const # = require(#);', [moduleVar, import.from]));
@@ skipping 16 matching lines @@
         var names = export.exportedNames;
         // export * is not emitted by the compiler, so we don't handle it here.
         assert(names != null);
         for (var name in names) {
           statements
               .add(js.statement('#.# = #;', [exportsVar, name.name, name]));
         }
       }
     }
 
-    // TODO(vsm): See https://github.com/dart-lang/sdk/issues/27309
-    // This extra level of indirection should be unnecessary.
-    var block =
-        js.statement("(function() { 'use strict'; #; })()", [statements]);
-
-    return new Program([block]);
+    return new Program(statements);
   }
 }
 
 /// Generates AMD modules (used in browsers with RequireJS).
 class AmdModuleBuilder extends _ModuleBuilder {
   final bool singleOutFile;
 
   AmdModuleBuilder({this.singleOutFile: false});
 
   Program build(Program module) {
@@ skipping 77 matching lines @@
   // Ensure the identifier first character is not numeric and that the whole
   // identifier is not a keyword.
   if (result.startsWith(new RegExp('[0-9]')) || invalidVariableName(result)) {
     return '\$$result';
   }
   return result;
 }
 
 // Invalid characters for identifiers, which would need to be escaped.
 final _invalidCharInIdentifier = new RegExp(r'[^A-Za-z_$0-9]');