Add browser tests for FetchEvent.request.mode/credentials in the service worker

chrome/test/data/nacl/pnacl_url_loader/pnacl_url_loader.html

Index: chrome/test/data/nacl/pnacl_url_loader/pnacl_url_loader.html
diff --git a/chrome/test/data/nacl/pnacl_url_loader/pnacl_url_loader.html b/chrome/test/data/nacl/pnacl_url_loader/pnacl_url_loader.html
new file mode 100644
index 0000000000000000000000000000000000000000..ef6347859b57668921237dbb02b167ae374b7f58
--- /dev/null
+++ b/chrome/test/data/nacl/pnacl_url_loader/pnacl_url_loader.html
@@ -0,0 +1,19 @@
+<script>
+window.addEventListener("load", function() {

[nhiroki, 2016/02/09 04:48:42]

nit: single-quotes (') are preferred to double-quotes (")

https://google.github.io/styleguide/javascriptguide.xml?showone=Strings#Strings

[horo, 2016/02/10 06:09:22]

Done.

+    init();
+  }, false);
+
+function init() {
+  var embed = document.createElement("embed");
+  embed.addEventListener("message", function(message) {
+      window.domAutomationController.setAutomationId(0);
+      window.domAutomationController.send(message.data);
+    }, false);
+  embed.addEventListener("load", function() {
+      embed.postMessage(location.hash.substr(1));
+    }, false);
+  embed.src = "pnacl_url_loader.nmf";
+  embed.type = "application/x-pnacl";
+  document.body.appendChild(embed);
+}
+</script>