Fix http://code.google.com/p/dart/issues/detail?id=15017.

sdk/lib/_internal/compiler/implementation/closure.dart

 // Copyright (c) 2012, 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 closureToClassMapper;
 
 import "elements/elements.dart";
 import "dart2jslib.dart";
 import "dart_types.dart";
 import "scanner/scannerlib.dart" show Token;
@@ skipping 74 matching lines @@
   }
 
   Expression get cachedNode {
     throw new SpannableAssertionFailure(
         variableElement,
         'Should not access cachedNode of ClosureFieldElement.');
   }
 
   bool isInstanceMember() => true;
   bool isAssignable() => false;
-  // The names of closure variables don't need renaming, since their use is very
-  // simple and they have 1-character names in the minified mode.
-  bool hasFixedBackendName() => true;
-  String fixedBackendName() => name;
 
   DartType computeType(Compiler compiler) {
     return variableElement.computeType(compiler);
   }
 
   String toString() => "ClosureFieldElement($name)";
 }
 
 // TODO(ahe): These classes continuously cause problems.  We need to
 // move these classes to elements/modelx.dart or see if we can find a
@@ skipping 721 matching lines @@
   }
 
   visitTryStatement(TryStatement node) {
     // TODO(ngeoffray): implement finer grain state.
     bool oldInTryStatement = inTryStatement;
     inTryStatement = true;
     node.visitChildren(this);
     inTryStatement = oldInTryStatement;
   }
 }