Bug 18597: Check that the Performance Observer API cannot be used

TBBTestSuite/TestSuite/BrowserBundleTests.pm

@@ -336,6 +336,17 @@ our @tests = (
         #    'dom.enable_user_timing' => 'true',
         #},
     },
+    {
+        name            => 'performance-observer',
+        type            => 'marionette',
+        descr           => 'Check that the Performance Observer API is really disabled',
+        use_net         => 1,
+        # To check that the test fails when performance observer is enabled,
+        # uncomment this:
+        #prefs           => {
+        #    'dom.enable_performance_observer' => 'true',
+        #},
+    },
     {
         name            => 'searchengines',
         type            => 'marionette',

marionette/tor_browser_tests/test_performance-observer.py

+# This test checks whether the Performance Observer API (see:
+# https://w3c.github.io/performance-timeline/#the-performanceobserver-interface)
+# is really disabled in the default Tor Browser.
+# Setting |dom.enable_performance_observer| to |false| and testing that
+# might not be sufficient.
+
+from marionette_driver import By
+from marionette_driver.errors import MarionetteException
+
+from marionette import MarionetteTestCase
+
+class Test(MarionetteTestCase):
+
+    def setUp(self):
+        MarionetteTestCase.setUp(self)
+
+        self.TEST_URL = "about:robots"
+
+
+    def test_performance_observer(self):
+
+        with self.marionette.using_context('content'):
+            self.marionette.navigate(self.TEST_URL)
+
+            err_msg = 'performance observer is working'
+            self.assertTrue(self.marionette.execute_script("""
+                var pass = false;
+                try {
+                        var observer = new PerformanceObserver(function(list) { });
+                        observer.observe({entryTypes: ['resource', 'mark', 'measure']});
+                } catch (e) {
+                        pass = true;
+                }
+                return pass;
+                """),
+                msg=err_msg)