dart2js: Fix hints in code base.

pkg/compiler/lib/src/elements/common.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.
 
 /// Mixins that implement convenience methods on [Element] subclasses.
 
 library elements.common;
 
 import '../dart2jslib.dart' show Compiler, isPrivateName;
 import '../dart_types.dart' show DartType, InterfaceType, FunctionType;
-import '../universe/universe.dart' show Selector;
 import '../util/util.dart' show Link;
 
 import 'elements.dart';
 
 abstract class ElementCommon implements Element {
   @override
   bool get isLibrary => kind == ElementKind.LIBRARY;
 
   @override
   bool get isCompilationUnit => kind == ElementKind.COMPILATION_UNIT;
@@ skipping 442 matching lines @@
       // this signature must not have more required parameters.  Having more
       // optional parameters is not a problem, they simply are never provided
       // by call sites of a call to a method with the other signature.
       int otherTotalCount = signature.parameterCount;
       return requiredParameterCount <= otherTotalCount
           && parameterCount >= otherTotalCount;
     }
     return true;
   }
 }