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diff --git a/toolkit/components/telemetry/app/TelemetryTimestamps.sys.mjs b/toolkit/components/telemetry/app/TelemetryTimestamps.sys.mjs
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+/* 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/. */
+
+/**
+ * This module's purpose is to collect timestamps for important
+ * application-specific events.
+ *
+ * The TelemetryController component attaches the timestamps stored by this module to
+ * the telemetry submission, substracting the process lifetime so that the times
+ * are relative to process startup. The overall goal is to produce a basic
+ * timeline of the startup process.
+ */
+var timeStamps = {};
+
+export var TelemetryTimestamps = {
+  /**
+   * Adds a timestamp to the list. The addition of TimeStamps that already have
+   * a value stored is ignored.
+   *
+   * @param name must be a unique, generally "camelCase" descriptor of what the
+   *             timestamp represents. e.g.: "delayedStartupStarted"
+   * @param value is a timeStamp in milliseconds since the epoch. If omitted,
+   *              defaults to Date.now().
+   */
+  add: function TT_add(name, value) {
+    // Default to "now" if not specified
+    if (value == null) {
+      value = Date.now();
+    }
+
+    if (isNaN(value)) {
+      throw new Error("Value must be a timestamp");
+    }
+
+    // If there's an existing value, just ignore the new value.
+    if (timeStamps.hasOwnProperty(name)) {
+      return;
+    }
+
+    timeStamps[name] = value;
+  },
+
+  /**
+   * Returns a JS object containing all of the timeStamps as properties (can be
+   * easily serialized to JSON). Used by TelemetryController to retrieve the data
+   * to attach to the telemetry submission.
+   */
+  get: function TT_get() {
+    // Return a copy of the object.
+    return Cu.cloneInto(timeStamps, {});
+  },
+};