diff -r 000000000000 -r 6474c204b198 dom/plugins/test/unit/test_plugin_default_state.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/plugins/test/unit/test_plugin_default_state.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+Components.utils.import("resource://gre/modules/Services.jsm");
+
+function run_test() {
+  let pluginDefaultState = Services.prefs.getIntPref("plugin.default.state");
+  // if this fails, we just have to switch around the values we're testing
+  do_check_neq(pluginDefaultState, Ci.nsIPluginTag.STATE_DISABLED);
+  let nonDefaultState = (pluginDefaultState != Ci.nsIPluginTag.STATE_ENABLED ?
+                         Ci.nsIPluginTag.STATE_ENABLED :
+                         Ci.nsIPluginTag.STATE_CLICKTOPLAY);
+  let ph = Cc["@mozilla.org/plugin/host;1"].getService(Ci.nsIPluginHost);
+  let testPlugin = get_test_plugintag();
+  // the test plugin should have the default enabledState
+  do_check_eq(testPlugin.enabledState, pluginDefaultState);
+
+  let secondTestPlugin = get_test_plugintag("Second Test Plug-in");
+  // set an enabledState for the second test plugin
+  secondTestPlugin.enabledState = Ci.nsIPluginTag.STATE_DISABLED;
+  // change what the default enabledState is
+  Services.prefs.setIntPref("plugin.default.state", nonDefaultState);
+  // the test plugin should follow the default (it has no individual pref yet)
+  do_check_eq(testPlugin.enabledState, nonDefaultState);
+  // the second test plugin should retain its preferred state
+  do_check_eq(secondTestPlugin.enabledState, Ci.nsIPluginTag.STATE_DISABLED);
+
+  // clean up
+  testPlugin.enabledState = pluginDefaultState;
+  secondTestPlugin.enabledState = pluginDefaultState;
+  Services.prefs.clearUserPref("plugin.default.state");
+  Services.prefs.clearUserPref("plugin.importedState");
+}