--- a/dom/media/tests/mochitest/moz.build
+++ b/dom/media/tests/mochitest/moz.build
@@ -1,6 +1,7 @@
 # -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
 # vim: set filetype=python:
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+WEBRTC_SIGNALLING_TEST_MANIFESTS += ['steeplechase.ini']

new file mode 100644
--- /dev/null
+++ b/dom/media/tests/mochitest/steeplechase.ini
@@ -0,0 +1,8 @@
+[DEFAULT]
+support-files =
+  head.js
+  mediaStreamPlayback.js
+  pc.js
+  templates.js
+
+[test_peerConnection_basicAudio.html]

--- a/python/mozbuild/mozbuild/frontend/emitter.py
+++ b/python/mozbuild/mozbuild/frontend/emitter.py
@@ -216,16 +216,17 @@ class TreeMetadataEmitter(LoggingMixin):
         # We ideally don't filter out inactive tests. However, not every test
         # harness can yet deal with test filtering. Once all harnesses can do
         # this, this feature can be dropped.
         test_manifests = dict(
             A11Y=('a11y', 'testing/mochitest/a11y', True),
             BROWSER_CHROME=('browser-chrome', 'testing/mochitest/browser', True),
             MOCHITEST=('mochitest', 'testing/mochitest/tests', True),
             MOCHITEST_CHROME=('chrome', 'testing/mochitest/chrome', True),
+            WEBRTC_SIGNALLING_TEST=('steeplechase', 'steeplechase', True),
             XPCSHELL_TESTS=('xpcshell', 'xpcshell', False),
         )
 
         for prefix, info in test_manifests.items():
             for path in sandbox.get('%s_MANIFESTS' % prefix, []):
                 for obj in self._process_test_manifest(sandbox, info, path):
                     yield obj
 

--- a/python/mozbuild/mozbuild/frontend/sandbox_symbols.py
+++ b/python/mozbuild/mozbuild/frontend/sandbox_symbols.py
@@ -462,16 +462,19 @@ VARIABLES = {
     'MOCHITEST_MANIFESTS': (StrictOrderingOnAppendList, list, [],
         """List of manifest files defining mochitest tests.
         """),
 
     'MOCHITEST_CHROME_MANIFESTS': (StrictOrderingOnAppendList, list, [],
         """List of manifest files defining mochitest chrome tests.
         """),
 
+    'WEBRTC_SIGNALLING_TEST_MANIFESTS': (StrictOrderingOnAppendList, list, [],
+        """List of manifest files defining WebRTC signalling tests."""),
+
     'XPCSHELL_TESTS_MANIFESTS': (StrictOrderingOnAppendList, list, [],
         """List of manifest files defining xpcshell tests.
         """),
 }
 
 # The set of functions exposed to the sandbox.
 #
 # Each entry is a tuple of: