All strong mode cleaning of dart2js.

pkg/compiler/lib/src/js_backend/no_such_method_registry.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 '../common.dart';
 import '../common_elements.dart' show CommonElements;
 import '../common/names.dart' show Identifiers, Selectors;
 import '../elements/entities.dart';
 import '../types/types.dart';
 
@@ skipping 177 matching lines @@
   NOT_APPLICABLE,
   OTHER,
 }
 
 /// Interface for determining the form of a `noSuchMethod` implementation.
 abstract class NoSuchMethodResolver {
   /// Computes whether [method] is of the form
   ///
   ///     noSuchMethod(i) => super.noSuchMethod(i);
   ///
-  bool hasForwardingSyntax(FunctionEntity method);
+  bool hasForwardingSyntax(covariant FunctionEntity method);
 
   /// Computes whether [method] is of the form
   ///
   ///     noSuchMethod(i) => throw new Error();
   ///
-  bool hasThrowingSyntax(FunctionEntity method);
+  bool hasThrowingSyntax(covariant FunctionEntity method);
 
   /// Returns the `noSuchMethod` that [method] overrides.
-  FunctionEntity getSuperNoSuchMethod(FunctionEntity method);
+  FunctionEntity getSuperNoSuchMethod(covariant FunctionEntity method);
 }