Implement reflecting on mixin applications.

dart/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class Namer implements ClosureNamer {
@@ skipping 523 matching lines @@
       // TODO(johnniwinther): Change factory name encoding as to not include
       // the class-name twice.
       String className = element.getEnclosingClass().name.slowToString();
       name = '${className}_${Elements.reconstructConstructorName(element)}';
     } else if (Elements.isStaticOrTopLevel(element)) {
       if (element.isMember()) {
         ClassElement enclosingClass = element.getEnclosingClass();
         name = "${enclosingClass.name.slowToString()}_"
                "${element.name.slowToString()}";
       } else {
-        name = element.name.slowToString();
+        name = element.name.slowToString().replaceAll('+', '_');
       }
     } else if (element.isLibrary()) {
       name = LIBRARY_PREFIX;
     } else {
       name = element.name.slowToString();
     }
     return name;
   }
 
   String getInterceptorSuffix(Iterable<ClassElement> classes) {
@@ skipping 707 matching lines @@
         if (!first) {
           sb.write('_');
         }
         sb.write('_');
         visit(link.head);
         first = true;
       }
     }
   }
 }