Avoid generating VariableUse nodes with non-identifier names

sdk/lib/_internal/compiler/implementation/js_emitter/reflection_data_parser.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.
 
 part of dart2js.js_emitter;
 
 // TODO(ahe): Share these with js_helper.dart.
 const FUNCTION_INDEX = 0;
 const NAME_INDEX = 1;
 const CALL_NAME_INDEX = 2;
 const REQUIRED_PARAMETER_INDEX = 3;
 const OPTIONAL_PARAMETER_INDEX = 4;
 const DEFAULT_ARGUMENTS_INDEX = 5;
 
 const bool VALIDATE_DATA = false;
 
 // TODO(ahe): This code should be integrated in CodeEmitterTask.finishClasses.
 jsAst.Expression getReflectionDataParser(String classesCollector,
                                         JavaScriptBackend backend) {
   Namer namer = backend.namer;
   Compiler compiler = backend.compiler;
   Element closureFromTearOff = compiler.findHelper('closureFromTearOff');
   String tearOffAccess;
   String tearOffGlobalObjectName;
   String tearOffGlobalObject;
   if (closureFromTearOff != null) {
+    // TODO(sra): Replace with AST.
     tearOffAccess = namer.isolateAccess(closureFromTearOff);
     tearOffGlobalObjectName = tearOffGlobalObject =
         namer.globalObjectFor(closureFromTearOff);
   } else {
     // Default values for mocked-up test libraries.
     tearOffAccess =
         r'''function() { throw 'Helper \'closureFromTearOff\' missing.' }''';
     tearOffGlobalObjectName = 'MissingHelperFunction';
     tearOffGlobalObject = '($tearOffAccess())';
   }
@@ skipping 313 matching lines @@
 (function() {
   var result = $array[$index];
   if ($check) {
     throw new Error(
         name + ": expected value of type \'$type\' at index " + ($index) +
         " but got " + (typeof result));
   }
   return result;
 })()''';
 }