predictors: Add browsertests that check fetching through javascript.

chrome/test/data/predictors/fetch.js

Index: chrome/test/data/predictors/fetch.js
diff --git a/chrome/test/data/predictors/fetch.js b/chrome/test/data/predictors/fetch.js
new file mode 100644
index 0000000000000000000000000000000000000000..b34301f6d1b942f1329cdbccdba64fbed5a8c5c2
--- /dev/null
+++ b/chrome/test/data/predictors/fetch.js
@@ -0,0 +1,7 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+fetch("/handled-by-test/image.png");
+fetch("/handled-by-test/style.css");
+fetch("/handled-by-test/script.js");