Remove AsyncError with Expando.

tests/html/fileapi_test.dart

 library fileapi;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:html';
 import 'dart:async';
 
 class FileAndDir {
   FileEntry file;
   DirectoryEntry dir;
   FileAndDir(this.file, this.dir);
@@ skipping 26 matching lines @@
     });
   });
 
   group('getDirectory', () {
     if (FileSystem.supported) {
       test('getFileSystem', getFileSystem);
 
       test('directoryDoesntExist', () {
         return fs.root.getDirectory(
             'directory2')
-              .catchError((e) {
-                expect(e.error.code, equals(FileError.NOT_FOUND_ERR));
+              .catchError((error) {
+                expect(error.code, equals(FileError.NOT_FOUND_ERR));
               }, test: (e) => e is FileError);
         });
 
       test('directoryCreate', () {
         return fs.root.createDirectory(
             'directory3')
               .then((DirectoryEntry e) {
                 expect(e.name, equals('directory3'));
               });
         });
     }
   });
 
   group('getFile', () {
     if (FileSystem.supported) {
       test('getFileSystem', getFileSystem);
 
       test('fileDoesntExist', () {
         return fs.root.getFile(
             'file2')
-          .catchError((e) {
-            expect(e.error.code, equals(FileError.NOT_FOUND_ERR));
+          .catchError((error) {
+            expect(error.code, equals(FileError.NOT_FOUND_ERR));
           }, test: (e) => e is FileError);
       });
 
       test('fileCreate', () {
         return fs.root.createFile(
             'file4')
           .then((FileEntry e) {
             expect(e.name, equals('file4'));
             expect(e.isFile, isTrue);
             return e.getMetadata();
@@ skipping 64 matching lines @@
       });
 
       test('moveTo', () {
         return doDirSetup()
           .then((fileAndDir) {
             return fileAndDir.file.moveTo(fileAndDir.dir, name: 'movedFile');
           }).then((entry) {
             expect(entry.name, 'movedFile');
             expect(entry.fullPath, '/directory3/movedFile');
             return fs.root.getFile('file4');
-          }).catchError((e) {
-            expect(e.error.code, equals(FileError.NOT_FOUND_ERR));
+          }).catchError((error) {
+            expect(error.code, equals(FileError.NOT_FOUND_ERR));
           }, test: (e) => e is FileError);
       });
 
       test('remove', () {
         return doDirSetup()
           .then((fileAndDir) {
             return fileAndDir.file.remove().then((_) {});
           });
       });
     }
@@ skipping 22 matching lines @@
                 expect(fileObj.name, fileAndDir.file.name);
                 expect(fileObj.relativePath, '');
                 expect(new DateTime.now().difference(
                     fileObj.lastModifiedDate).inSeconds, lessThan(60));
               });
           });
       });
     }
   });
 }