Shorter encoding for zero optional arguments.

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.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.
 
 part of dart2js.js_emitter.startup_emitter.model_emitter;
 
 /// The name of the property that stores the tear-off getter on a static
 /// function.
 ///
 /// This property is only used when isolates are used.
@@ skipping 815 matching lines @@
     }
     return new js.Block(assignments);
   }
 
   /// Encodes the optional default values so that the runtime Function.apply
   /// can use them.
   js.Expression _encodeOptionalParameterDefaultValues(DartMethod method) {
     // TODO(herhut): Replace [js.LiteralNull] with [js.ArrayHole].
     if (method.optionalParameterDefaultValues is List) {
       List<ConstantValue> defaultValues = method.optionalParameterDefaultValues;
+      if (defaultValues.isEmpty) {
+        return new js.LiteralNull();
+      }
       Iterable<js.Expression> elements =
           defaultValues.map(generateConstantReference);
       return js.js('function() { return #; }',
           new js.ArrayInitializer(elements.toList()));
     } else {
       Map<String, ConstantValue> defaultValues =
           method.optionalParameterDefaultValues;
       List<js.Property> properties = <js.Property>[];
       List<String> names = defaultValues.keys.toList(growable: false);
       // Sort the names the same way we sort them for the named-argument calling
@@ skipping 465 matching lines @@
     }
     statements.add(js.js.statement("setOrUpdateInterceptorsByTag(#);",
         js.objectLiteral(interceptorsByTag)));
     statements.add(
         js.js.statement("setOrUpdateLeafTags(#);", js.objectLiteral(leafTags)));
     statements.add(subclassAssignment);
 
     return new js.Block(statements);
   }
 }