Prepare for handling super noSuchMethod

pkg/compiler/lib/src/kernel/element_map_impl.dart

 // Copyright (c) 2017, 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 dart2js.kernel.element_map;
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../closure.dart' show BoxLocal;
 import '../common.dart';
@@ skipping 348 matching lines @@
     IndexedClass superclass = _getSuperType(cls)?.element;
     while (superclass != null) {
       ClassEnv env = _classEnvs[superclass.classIndex];
       MemberEntity superMember =
           env.lookupMember(this, name.name, setter: setter);
       if (superMember != null) {
         return superMember;
       }
       superclass = _getSuperType(superclass)?.element;
     }
-    throw failedAt(cls, "No super method member found for ${name} in $cls.");
+    return null;
   }
 
   @override
   ConstructorEntity getConstructor(ir.Member node) => _getConstructor(node);
 
   ConstructorEntity _getConstructor(ir.Member node);
 
   ConstructorEntity getSuperConstructor(
       ir.Constructor sourceNode, ir.Member targetNode) {
     ConstructorEntity source = getConstructor(sourceNode);
@@ skipping 1941 matching lines @@
   ///
   /// These names are not used in generated code, just as element name.
   String _getClosureVariableName(String name, int id) {
     return "_captured_${name}_$id";
   }
 
   String getDeferredUri(ir.LibraryDependency node) {
     throw new UnimplementedError('JsKernelToElementMap.getDeferredUri');
   }
 }