1 files changed, 45 insertions, 0 deletions
diff --git a/browser/components/syncedtabs/EventEmitter.jsm b/browser/components/syncedtabs/EventEmitter.jsm
new file mode 100644
index 000000000..ec3225f0f
--- /dev/null
+++ b/browser/components/syncedtabs/EventEmitter.jsm
@@ -0,0 +1,45 @@
+/* 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 {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+this.EXPORTED_SYMBOLS = [
+  "EventEmitter"
+];
+
+// Simple event emitter abstraction for storage objects to use.
+function EventEmitter () {
+  this._events = new Map();
+}
+
+EventEmitter.prototype = {
+  on(event, listener) {
+    if (this._events.has(event)) {
+      this._events.get(event).add(listener);
+    } else {
+      this._events.set(event, new Set([listener]));
+    }
+  },
+  off(event, listener) {
+    if (!this._events.has(event)) {
+      return;
+    }
+    this._events.get(event).delete(listener);
+  },
+  emit(event, ...args) {
+    if (!this._events.has(event)) {
+      return;
+    }
+    for (let listener of this._events.get(event).values()) {
+      try {
+        listener.apply(this, args);
+      } catch (e) {
+        Cu.reportError(e);
+      }
+    }
+  },
+};
+