1 files changed, 24 insertions, 0 deletions
diff --git a/devtools/client/shared/redux/middleware/xpcshell/head.js b/devtools/client/shared/redux/middleware/xpcshell/head.js
new file mode 100644
index 0000000000..5bd44c0030
--- /dev/null
+++ b/devtools/client/shared/redux/middleware/xpcshell/head.js
@@ -0,0 +1,24 @@
+/* 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/. */
+
+/* exported waitUntilState */
+
+"use strict";
+
+const { require } = ChromeUtils.import("resource://devtools/shared/Loader.jsm");
+
+function waitUntilState(store, predicate) {
+  return new Promise(resolve => {
+    const unsubscribe = store.subscribe(check);
+    function check() {
+      if (predicate(store.getState())) {
+        unsubscribe();
+        resolve();
+      }
+    }
+
+    // Fire the check immediately incase the action has already occurred
+    check();
+  });
+}