diff -r 000000000000 -r 6474c204b198 browser/base/content/test/general/head_plain.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/test/general/head_plain.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,27 @@
+
+function getTestPlugin(pluginName) {
+  var ph = SpecialPowers.Cc["@mozilla.org/plugin/host;1"]
+                                 .getService(SpecialPowers.Ci.nsIPluginHost);
+  var tags = ph.getPluginTags();
+  var name = pluginName || "Test Plug-in";
+  for (var tag of tags) {
+    if (tag.name == name) {
+      return tag;
+    }
+  }
+
+  ok(false, "Could not find plugin tag with plugin name '" + name + "'");
+  return null;
+}
+
+// call this to set the test plugin(s) initially expected enabled state.
+// it will automatically be reset to it's previous value after the test
+// ends
+function setTestPluginEnabledState(newEnabledState, pluginName) {
+  var plugin = getTestPlugin(pluginName);
+  var oldEnabledState = plugin.enabledState;
+  plugin.enabledState = newEnabledState;
+  SimpleTest.registerCleanupFunction(function() {
+    getTestPlugin(pluginName).enabledState = oldEnabledState;
+  });
+}