Add a larger time window for file creation test.

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 66 matching lines @@
       test('fileCreate', () {
         return fs.root.getFile(
             'file4',
             options: {'create': true})
           .then((FileEntry e) {
             expect(e.name, equals('file4'));
             expect(e.isFile, isTrue);
             return e.getMetadata();
           }).then((Metadata metadata) {
             var changeTime = metadata.modificationTime;
-            expect(new DateTime.now().difference(changeTime).inSeconds,
-                lessThan(60));
+            // Upped because our Windows buildbots can sometimes be particularly
+            // slow.
+            expect(new DateTime.now().difference(changeTime).inMinutes,
+                lessThan(4));
             expect(metadata.size, equals(0));
           });
         });
     }
   });
 
   // Do the boilerplate to get several files and directories created to then
   // test the functions that use those items.
   Future doDirSetup() {
     return fs.root.getFile(
@@ skipping 94 matching lines @@
                 expect(fileObj.name, fileAndDir.file.name);
                 expect(fileObj.relativePath, '');
                 expect(new DateTime.now().difference(
                     fileObj.lastModifiedDate).inSeconds, lessThan(60));
               });
           });
       });
     }
   });
 }