Use JS backend in serialization_analysis_test

pkg/compiler/lib/src/elements/modelx.dart

 // Copyright (c) 2013, 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 elements.modelx;
 
 import '../common.dart';
 import '../common/resolution.dart' show
     Resolution,
     Parsing;
@@ skipping 190 matching lines @@
     // the outermost for elements in closure classses, but some call-sites rely
     // on that behavior.
     for (Element e = this; e != null; e = e.enclosingElement) {
       if (e.isClassMember || e.isTopLevel) {
         return e;
       }
     }
     return null;
   }
 
-  ClassElement get contextClass {
-    ClassElement cls;
-    for (Element e = this; e != null; e = e.enclosingElement) {
-      if (e.isClass) {
-        // Record [e] instead of returning it directly. We need the last class
-        // in the chain since the first classes might be closure classes.
-        cls = e.declaration;
-      }
-    }
-    return cls;
-  }
-
   /**
    * Creates the scope for this element.
    */
   Scope buildScope() => enclosingElement.buildScope();
 
   String toString() {
     // TODO(johnniwinther): Test for nullness of name, or make non-nullness an
     // invariant for all element types?
     var nameText = name != null ? name : '?';
     if (enclosingElement != null && !isTopLevel) {
@@ skipping 2988 matching lines @@
   AstElement get definingElement;
 
   bool get hasResolvedAst => definingElement.hasTreeElements;
 
   ResolvedAst get resolvedAst {
     return new ResolvedAst(declaration,
         definingElement.node, definingElement.treeElements);
   }
 
 }