Avoid syntax errors on oddly named fields.

dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.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.
 
 part of js_backend;
 
 /**
  * A function element that represents a closure call. The signature is copied
  * from the given element.
  */
@@ skipping 294 matching lines @@
 
       js.if_(js('typeof fields == "function"'), [
         js('constructor = fields')
       ], /* else */ [
         js('var str = "function " + cls + "("'),
         js('var body = ""'),
 
         js.for_('var i = 0', 'i < fields.length', 'i++', [
           js.if_('i != 0', js('str += ", "')),
 
-          js('var field = fields[i]'),
-          js('field = generateAccessor(field, prototype)'),
-          js('str += field'),
-          js('body += ("this." + field + " = " + field + ";\\n")')
+          js('var field = generateAccessor(fields[i], prototype)'),
+          js('var parameter = "parameter_" + field'),
+          js('str += parameter'),
+          js('body += ("this." + field + " = " + parameter + ";\\n")')
         ]),
 
         js('str += (") {" + body + "}\\nreturn " + cls)'),
 
         js('constructor = new Function(str)()')
       ]),
 
       js('constructor.prototype = prototype'),
       js(r'constructor.builtin$cls = name'),
 
@@ skipping 2816 matching lines @@
 """;
 const String HOOKS_API_USAGE = """
 // The code supports the following hooks:
 // dartPrint(message)   - if this function is defined it is called
 //                        instead of the Dart [print] method.
 // dartMainRunner(main) - if this function is defined, the Dart [main]
 //                        method will not be invoked directly.
 //                        Instead, a closure that will invoke [main] is
 //                        passed to [dartMainRunner].
 """;