Align synthetic mixin names with fasta.

pkg/compiler/lib/src/resolution/class_hierarchy.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.
 
 library dart2js.resolution.class_hierarchy;
 
 import '../common.dart';
 import '../common/resolution.dart' show Resolution;
 import '../common_elements.dart' show CommonElements;
 import '../elements/resolution_types.dart';
@@ skipping 429 matching lines @@
         if (lastAndNamed) {
           mixinElement = element;
           variables = freeTypes;
         } else {
           String signature = computeSignature(signatureIndex);
           name = supertype.name;
           int index = name.indexOf("^");
           if (index != -1) {
             name = name.substring(0, index);
           }
-          name = "$name&${mixin.name}$signature";
+          name = "_$name&${mixin.name}$signature";
           mixinElement = mixinApplicationClasses[name];
           if (mixinElement != null) return mixinElement.thisType;
 
           mixinElement = new UnnamedMixinApplicationElementX(
               name, element, resolution.idGenerator.getNextFreeId(), node);
           variables = computeTypeVariables(mixinElement, node);
           mixinElement.setThisAndRawTypes(variables.values.toList());
           mixinApplicationClasses[name] = mixinElement;
         }
 
@@ skipping 397 matching lines @@
     Identifier selector = node.selector.asIdentifier();
     var e = prefixElement.lookupLocalMember(selector.source);
     if (e == null || !e.impliesType) {
       reporter.reportErrorMessage(node.selector,
           MessageKind.CANNOT_RESOLVE_TYPE, {'typeName': node.selector});
       return;
     }
     loadSupertype(e, node);
   }
 }