Fix csp mode on platforms that don't support __proto__.

pkg/compiler/lib/src/js_emitter/full_emitter/setup_program_builder.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.full_emitter;
 
 // TODO(ahe): Share these with js_helper.dart.
 const FUNCTION_INDEX = 0;
 const NAME_INDEX = 1;
 const CALL_NAME_INDEX = 2;
@@ skipping 481 matching lines @@
       // handler on [mixinPrototype] and then resumes handling on
       // [targetPrototype]. If [targetPrototype] already has a handler
       // installed, the handler is preserved in the generated closure and
       // thus can be safely overwritten.
       function mixinDeferredActionHelper(mixinPrototype, targetPrototype) {
         var chain;
         if (targetPrototype.hasOwnProperty(#deferredActionString)) {
           chain = targetPrototype.#deferredAction;
         }
         return function foo() {
+          if (!supportsDirectProtoAccess) return;
           var prototype = this;
           // Find the actual prototype that this handler is installed on.
           while (!prototype.hasOwnProperty(#deferredActionString)) {
             prototype = prototype.__proto__;
           }
           if (chain) {
             prototype.#deferredAction = chain;
           } else {
             delete prototype.#deferredAction;
             convertToFastObject(prototype);
@@ skipping 342 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;
 })()''';
 }