Remove deprecated string features.

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 178 matching lines @@
     return (js[variable] & RENAMING_FLAG).notEquals(0);
   }
 
   jsAst.FunctionDeclaration get generateAccessorFunction {
     // function generateAccessor(field, prototype) {
     jsAst.Fun fun = js.fun(['field', 'prototype'], [
 
       // var len = field.length;
       js['len'].def(js['field']['length']),
 
-      // var lastCharCode = field.charCodeAt(len - 1);
+      // var lastCharCode = field.codeUnitAt(len - 1);
       js['lastCharCode'].def(js['field']['charCodeAt'](js['len'] - 1)),
 
       // var needsAccessor =
       //     (lastCharCode & $SUFFIX_MASK) >= $FIRST_SUFFIX_CODE;
       js['needsAccessor'].def(
           (js['lastCharCode'] & SUFFIX_MASK) >= FIRST_SUFFIX_CODE),
 
       // if (needsAccessor) {
       js.if_('needsAccessor', [
         // var needsGetter = ${needsGetterCode('lastCharCode')};
@@ skipping 2466 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].
 """;