Add a larger time window for file creation test.

tests/html/fileapi_test.dart

Index: tests/html/fileapi_test.dart
diff --git a/tests/html/fileapi_test.dart b/tests/html/fileapi_test.dart
index a089a3233b56e74351fceb17bcc495a80617ddd6..681750cffb1a990433c8439181135d10851f3f7d 100644
--- a/tests/html/fileapi_test.dart
+++ b/tests/html/fileapi_test.dart
@@ -84,8 +84,10 @@ main() {
             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));
           });
         });