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diff --git a/devtools/shared/worker/worker.sys.mjs b/devtools/shared/worker/worker.sys.mjs
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+++ b/devtools/shared/worker/worker.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/. */
+
+/* global ChromeWorker */
+
+let MESSAGE_COUNTER = 0;
+
+function dumpn(_msg) {
+  // dump(msg + "\n");
+}
+
+/**
+ * Creates a wrapper around a ChromeWorker, providing easy
+ * communication to offload demanding tasks. The corresponding URL
+ * must implement the interface provided by `devtools/shared/worker/helper`.
+ *
+ * @param {string} url
+ *        The URL of the worker.
+ * @param Object opts
+ *        An option with the following optional fields:
+ *        - name: a name that will be printed with logs
+ *        - verbose: log incoming and outgoing messages
+ */
+export function DevToolsWorker(url, opts) {
+  opts = opts || {};
+  this._worker = new ChromeWorker(url);
+  this._verbose = opts.verbose;
+  this._name = opts.name;
+
+  this._worker.addEventListener("error", this.onError);
+}
+
+/**
+ * Performs the given task in a chrome worker, passing in data.
+ * Returns a promise that resolves when the task is completed, resulting in
+ * the return value of the task.
+ *
+ * @param {string} task
+ *        The name of the task to execute in the worker.
+ * @param {any} data
+ *        Data to be passed into the task implemented by the worker.
+ * @param {undefined|Array} transfer
+ *        Optional array of transferable objects to transfer ownership of.
+ * @return {Promise}
+ */
+DevToolsWorker.prototype.performTask = function (task, data, transfer) {
+  if (this._destroyed) {
+    return Promise.reject(
+      "Cannot call performTask on a destroyed DevToolsWorker"
+    );
+  }
+  const worker = this._worker;
+  const id = ++MESSAGE_COUNTER;
+  const payload = { task, id, data };
+
+  if (this._verbose && dumpn) {
+    dumpn(
+      "Sending message to worker" +
+        (this._name ? " (" + this._name + ")" : "") +
+        ": " +
+        JSON.stringify(payload, null, 2)
+    );
+  }
+  worker.postMessage(payload, transfer);
+
+  return new Promise((resolve, reject) => {
+    const listener = ({ data: result }) => {
+      if (this._verbose && dumpn) {
+        dumpn(
+          "Received message from worker" +
+            (this._name ? " (" + this._name + ")" : "") +
+            ": " +
+            JSON.stringify(result, null, 2)
+        );
+      }
+
+      if (result.id !== id) {
+        return;
+      }
+      worker.removeEventListener("message", listener);
+      if (result.error) {
+        reject(result.error);
+      } else {
+        resolve(result.response);
+      }
+    };
+
+    worker.addEventListener("message", listener);
+  });
+};
+
+/**
+ * Terminates the underlying worker. Use when no longer needing the worker.
+ */
+DevToolsWorker.prototype.destroy = function () {
+  this._worker.terminate();
+  this._worker = null;
+  this._destroyed = true;
+};
+
+DevToolsWorker.prototype.onError = function ({ message, filename, lineno }) {
+  dump(new Error(message + " @ " + filename + ":" + lineno) + "\n");
+};
+
+/**
+ * Takes a function and returns a Worker-wrapped version of the same function.
+ * Returns a promise upon resolution.
+ * @see `./devtools/shared/shared/tests/browser/browser_devtools-worker-03.js
+ *
+ * ⚠ This should only be used for tests or A/B testing performance ⚠
+ *
+ * The original function must:
+ *
+ * Be a pure function, that is, not use any variables not declared within the
+ * function, or its arguments.
+ *
+ * Return a value or a promise.
+ *
+ * Note any state change in the worker will not affect the callee's context.
+ *
+ * @param {function} fn
+ * @return {function}
+ */
+export function workerify(fn) {
+  console.warn(
+    "`workerify` should only be used in tests or measuring performance. " +
+      "This creates an object URL on the browser window, and should not be " +
+      "used in production."
+  );
+  // Fetch modules here as we don't want to include it normally.
+  const { URL, Blob } = Services.wm.getMostRecentWindow("navigator:browser");
+  const stringifiedFn = createWorkerString(fn);
+  const blob = new Blob([stringifiedFn]);
+  const url = URL.createObjectURL(blob);
+  const worker = new DevToolsWorker(url);
+
+  const wrapperFn = (data, transfer) =>
+    worker.performTask("workerifiedTask", data, transfer);
+
+  wrapperFn.destroy = function () {
+    URL.revokeObjectURL(url);
+    worker.destroy();
+  };
+
+  return wrapperFn;
+}
+
+/**
+ * Takes a function, and stringifies it, attaching the worker-helper.js
+ * boilerplate hooks.
+ */
+function createWorkerString(fn) {
+  return `importScripts("resource://gre/modules/workers/require.js");
+          const { createTask } = require("resource://devtools/shared/worker/helper.js");
+          createTask(self, "workerifiedTask", ${fn.toString()});`;
+}