1 files changed, 40 insertions, 0 deletions
diff --git a/devtools/client/styleeditor/utils.js b/devtools/client/styleeditor/utils.js
new file mode 100644
index 000000000..6cb1aa8cc
--- /dev/null
+++ b/devtools/client/styleeditor/utils.js
@@ -0,0 +1,40 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* 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/. */
+
+"use strict";
+
+const Services = require("Services");
+const EventEmitter = require("devtools/shared/event-emitter");
+
+exports.PREF_ORIG_SOURCES = "devtools.styleeditor.source-maps-enabled";
+
+/**
+ * A PreferenceObserver observes a pref branch for pref changes.
+ * It emits an event for each preference change.
+ */
+function PrefObserver(branchName) {
+  this.branchName = branchName;
+  this.branch = Services.prefs.getBranch(branchName);
+  this.branch.addObserver("", this, false);
+
+  EventEmitter.decorate(this);
+}
+
+exports.PrefObserver = PrefObserver;
+
+PrefObserver.prototype = {
+  observe: function (subject, topic, data) {
+    if (topic == "nsPref:changed") {
+      this.emit(this.branchName + data);
+    }
+  },
+
+  destroy: function () {
+    if (this.branch) {
+      this.branch.removeObserver("", this);
+    }
+  }
+};