Do not suppress implicit constructors that need a super call.

lib/src/codegen/js_codegen.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.
 
 library dev_compiler.src.codegen.js_codegen;
 
 import 'dart:collection' show HashSet, HashMap;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/src/generated/ast.dart' hide ConstantEvaluator;
@@ skipping 664 matching lines @@
     ]);
   }
 
   /// Generates the implicit default constructor for class C of the form
   /// `C() : super() {}`.
   JS.Method _emitImplicitConstructor(
       ClassDeclaration node, String name, List<FieldDeclaration> fields) {
     assert(_hasUnnamedConstructor(node.element) == fields.isNotEmpty);
 
     // If we don't have a method body, skip this.
-    if (fields.isEmpty) return null;
+    var superCall = _superConstructorCall(node);
+    if (fields.isEmpty && superCall == null) return null;
 
     dynamic body = _initializeFields(fields);
-    var superCall = _superConstructorCall(node);
     if (superCall != null) body = [[body, superCall]];
     return new JS.Method(
         _propertyName(name), js.call('function() { #; }', body));
   }
 
   JS.Method _emitConstructor(ConstructorDeclaration node, String className,
       List<FieldDeclaration> fields, bool isObject) {
     if (_externalOrNative(node)) return null;
 
     var name = _constructorName(className, node.name);
@@ skipping 1839 matching lines @@
 // TODO(jmesserly): validate the library. See issue #135.
 bool _isJsNameAnnotation(DartObjectImpl value) => value.type.name == 'JsName';
 
 bool _isJsPeerInterface(DartObjectImpl value) =>
     value.type.name == 'JsPeerInterface';
 
 // TODO(jacobr): we would like to do something like the following
 // but we don't have summary support yet.
 // bool _supportJsExtensionMethod(AnnotatedNode node) =>
 //    _getAnnotation(node, "SupportJsExtensionMethod") != null;