1 files changed, 37 insertions, 0 deletions
diff --git a/toolkit/modules/ResponsivenessMonitor.jsm b/toolkit/modules/ResponsivenessMonitor.jsm
new file mode 100644
index 000000000..f84c6d837
--- /dev/null
+++ b/toolkit/modules/ResponsivenessMonitor.jsm
@@ -0,0 +1,37 @@
+/* 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";
+
+this.EXPORTED_SYMBOLS = ["ResponsivenessMonitor"];
+
+const { classes: Cc, interfaces: Ci } = Components;
+
+function ResponsivenessMonitor(intervalMS = 100) {
+  this._intervalMS = intervalMS;
+  this._prevTimestamp = Date.now();
+  this._accumulatedDelay = 0;
+  this._timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+  this._timer.initWithCallback(this, this._intervalMS, Ci.nsITimer.TYPE_REPEATING_SLACK);
+}
+
+ResponsivenessMonitor.prototype = {
+  notify() {
+    let now = Date.now();
+    this._accumulatedDelay += Math.max(0, now - this._prevTimestamp - this._intervalMS);
+    this._prevTimestamp = now;
+  },
+
+  abort() {
+    if (this._timer) {
+      this._timer.cancel();
+      this._timer = null;
+    }
+  },
+
+  finish() {
+    this.abort();
+    return this._accumulatedDelay;
+  },
+};