predictors: Add browsertests that check fetching through javascript.

chrome/test/data/predictors/document_write.js

Index: chrome/test/data/predictors/document_write.js
diff --git a/chrome/test/data/predictors/document_write.js b/chrome/test/data/predictors/document_write.js
new file mode 100644
index 0000000000000000000000000000000000000000..db7b817f5f980f9c141d648569d539dbbb615c72
--- /dev/null
+++ b/chrome/test/data/predictors/document_write.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.
+
+document.write('<img src="/handled-by-test/image.png">');
+document.write('<link rel="stylesheet" href="/handled-by-test/style.css">');
+document.write('<script src="/handled-by-test/script.js"></script>');