6 files changed, 776 insertions, 0 deletions
diff --git a/devtools/server/startup/content-process-script.js b/devtools/server/startup/content-process-script.js
new file mode 100644
index 0000000000..628c481685
--- /dev/null
+++ b/devtools/server/startup/content-process-script.js
@@ -0,0 +1,281 @@
+/* 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/. */
+
+/* eslint-env mozilla/process-script */
+
+"use strict";
+
+/**
+ * Main entry point for DevTools in content processes.
+ *
+ * This module is loaded early when a content process is started.
+ * Note that (at least) JS XPCOM registered at app-startup, will be running before.
+ * It is used by the multiprocess browser toolbox in order to debug privileged resources.
+ * When debugging a Web page loaded in a Tab, DevToolsFrame JS Window Actor is used instead
+ * (DevToolsFrameParent.jsm and DevToolsFrameChild.jsm).
+ *
+ * This module won't do anything unless DevTools codebase starts adding some data
+ * in `Services.cpmm.sharedData` object or send a message manager message via `Services.cpmm`.
+ * Also, this module is only loaded, on-demand from process-helper if devtools are watching for process targets.
+ */
+
+const SHARED_DATA_KEY_NAME = "DevTools:watchedPerWatcher";
+
+class ContentProcessStartup {
+  constructor() {
+    // The map is indexed by the Watcher Actor ID.
+    // The values are objects containing the following properties:
+    // - connection: the DevToolsServerConnection itself
+    // - actor: the ContentProcessTargetActor instance
+    this._connections = new Map();
+
+    this.observe = this.observe.bind(this);
+    this.receiveMessage = this.receiveMessage.bind(this);
+
+    this.addListeners();
+    this.maybeCreateExistingTargetActors();
+  }
+
+  observe(subject, topic, data) {
+    switch (topic) {
+      case "xpcom-shutdown": {
+        this.destroy();
+        break;
+      }
+    }
+  }
+
+  destroy(options) {
+    this.removeListeners();
+
+    for (const [, connectionInfo] of this._connections) {
+      connectionInfo.connection.close(options);
+    }
+    this._connections.clear();
+  }
+
+  addListeners() {
+    Services.obs.addObserver(this.observe, "xpcom-shutdown");
+
+    Services.cpmm.addMessageListener(
+      "debug:instantiate-already-available",
+      this.receiveMessage
+    );
+    Services.cpmm.addMessageListener(
+      "debug:destroy-target",
+      this.receiveMessage
+    );
+    Services.cpmm.addMessageListener(
+      "debug:add-session-data-entry",
+      this.receiveMessage
+    );
+    Services.cpmm.addMessageListener(
+      "debug:remove-session-data-entry",
+      this.receiveMessage
+    );
+    Services.cpmm.addMessageListener(
+      "debug:destroy-process-script",
+      this.receiveMessage
+    );
+  }
+
+  removeListeners() {
+    Services.obs.removeObserver(this.observe, "xpcom-shutdown");
+
+    Services.cpmm.removeMessageListener(
+      "debug:instantiate-already-available",
+      this.receiveMessage
+    );
+    Services.cpmm.removeMessageListener(
+      "debug:destroy-target",
+      this.receiveMessage
+    );
+    Services.cpmm.removeMessageListener(
+      "debug:add-session-data-entry",
+      this.receiveMessage
+    );
+    Services.cpmm.removeMessageListener(
+      "debug:remove-session-data-entry",
+      this.receiveMessage
+    );
+    Services.cpmm.removeMessageListener(
+      "debug:destroy-process-script",
+      this.receiveMessage
+    );
+  }
+
+  receiveMessage(msg) {
+    switch (msg.name) {
+      case "debug:instantiate-already-available":
+        this.createTargetActor(
+          msg.data.watcherActorID,
+          msg.data.connectionPrefix,
+          msg.data.sessionData,
+          true
+        );
+        break;
+      case "debug:destroy-target":
+        this.destroyTarget(msg.data.watcherActorID);
+        break;
+      case "debug:add-session-data-entry":
+        this.addSessionDataEntry(
+          msg.data.watcherActorID,
+          msg.data.type,
+          msg.data.entries
+        );
+        break;
+      case "debug:remove-session-data-entry":
+        this.removeSessionDataEntry(
+          msg.data.watcherActorID,
+          msg.data.type,
+          msg.data.entries
+        );
+        break;
+      case "debug:destroy-process-script":
+        this.destroy(msg.data.options);
+        break;
+      default:
+        throw new Error(`Unsupported message name ${msg.name}`);
+    }
+  }
+
+  /**
+   * Called when the content process just started.
+   * This will start creating ContentProcessTarget actors, but only if DevTools code (WatcherActor / WatcherRegistry.jsm)
+   * put some data in `sharedData` telling us to do so.
+   */
+  maybeCreateExistingTargetActors() {
+    const { sharedData } = Services.cpmm;
+
+    // Accessing `sharedData` right off the app-startup returns null.
+    // Spinning the event loop with dispatchToMainThread seems enough,
+    // but it means that we let some more Javascript code run before
+    // instantiating the target actor.
+    // So we may miss a few resources and will register the breakpoints late.
+    if (!sharedData) {
+      Services.tm.dispatchToMainThread(
+        this.maybeCreateExistingTargetActors.bind(this)
+      );
+      return;
+    }
+
+    const sessionDataByWatcherActor = sharedData.get(SHARED_DATA_KEY_NAME);
+    if (!sessionDataByWatcherActor) {
+      return;
+    }
+
+    // Create one Target actor for each prefix/client which listen to process
+    for (const [watcherActorID, sessionData] of sessionDataByWatcherActor) {
+      const { connectionPrefix, targets } = sessionData;
+      // This is where we only do something significant only if DevTools are opened
+      // and requesting to create target actor for content processes
+      if (targets?.includes("process")) {
+        this.createTargetActor(watcherActorID, connectionPrefix, sessionData);
+      }
+    }
+  }
+
+  /**
+   * Instantiate a new ContentProcessTarget for the given connection.
+   * This is where we start doing some significant computation that only occurs when DevTools are opened.
+   *
+   * @param String watcherActorID
+   *        The ID of the WatcherActor who requested to observe and create these target actors.
+   * @param String parentConnectionPrefix
+   *        The prefix of the DevToolsServerConnection of the Watcher Actor.
+   *        This is used to compute a unique ID for the target actor.
+   * @param Object sessionData
+   *        All data managed by the Watcher Actor and WatcherRegistry.jsm, containing
+   *        target types, resources types to be listened as well as breakpoints and any
+   *        other data meant to be shared across processes and threads.
+   * @param Object options Dictionary with optional values:
+   * @param Boolean options.ignoreAlreadyCreated
+   *        If true, do not throw if the target actor has already been created.
+   */
+  createTargetActor(
+    watcherActorID,
+    parentConnectionPrefix,
+    sessionData,
+    ignoreAlreadyCreated = false
+  ) {
+    if (this._connections.get(watcherActorID)) {
+      if (ignoreAlreadyCreated) {
+        return;
+      }
+      throw new Error(
+        "ContentProcessStartup createTargetActor was called more than once" +
+          ` for the Watcher Actor (ID: "${watcherActorID}")`
+      );
+    }
+    // Compute a unique prefix, just for this content process,
+    // which will be used to create a ChildDebuggerTransport pair between content and parent processes.
+    // This is slightly hacky as we typicaly compute Prefix and Actor ID via `DevToolsServerConnection.allocID()`,
+    // but here, we can't have access to any DevTools connection as we are really early in the content process startup
+    const prefix =
+      parentConnectionPrefix + "contentProcess" + Services.appinfo.processID;
+    //TODO: probably merge content-process.jsm with this module
+    const { initContentProcessTarget } = ChromeUtils.importESModule(
+      "resource://devtools/server/startup/content-process.sys.mjs"
+    );
+    const { actor, connection } = initContentProcessTarget({
+      target: Services.cpmm,
+      data: {
+        watcherActorID,
+        parentConnectionPrefix,
+        prefix,
+        sessionContext: sessionData.sessionContext,
+      },
+    });
+    this._connections.set(watcherActorID, {
+      actor,
+      connection,
+    });
+
+    // Pass initialization data to the target actor
+    for (const type in sessionData) {
+      actor.addSessionDataEntry(type, sessionData[type]);
+    }
+  }
+
+  destroyTarget(watcherActorID) {
+    const connectionInfo = this._connections.get(watcherActorID);
+    // This connection has already been cleaned?
+    if (!connectionInfo) {
+      throw new Error(
+        `Trying to destroy a content process target actor that doesn't exists, or has already been destroyed. Watcher Actor ID:${watcherActorID}`
+      );
+    }
+    connectionInfo.connection.close();
+    this._connections.delete(watcherActorID);
+  }
+
+  async addSessionDataEntry(watcherActorID, type, entries) {
+    const connectionInfo = this._connections.get(watcherActorID);
+    if (!connectionInfo) {
+      throw new Error(
+        `No content process target actor for this Watcher Actor ID:"${watcherActorID}"`
+      );
+    }
+    const { actor } = connectionInfo;
+    await actor.addSessionDataEntry(type, entries);
+    Services.cpmm.sendAsyncMessage("debug:add-session-data-entry-done", {
+      watcherActorID,
+    });
+  }
+
+  removeSessionDataEntry(watcherActorID, type, entries) {
+    const connectionInfo = this._connections.get(watcherActorID);
+    if (!connectionInfo) {
+      return;
+    }
+    const { actor } = connectionInfo;
+    actor.removeSessionDataEntry(type, entries);
+  }
+}
+
+// Only start this component for content processes.
+// i.e. explicitely avoid running it for the parent process
+if (Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT) {
+  new ContentProcessStartup();
+}
diff --git a/devtools/server/startup/content-process.js b/devtools/server/startup/content-process.js
new file mode 100644
index 0000000000..5710220e44
--- /dev/null
+++ b/devtools/server/startup/content-process.js
@@ -0,0 +1,33 @@
+/* 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/. */
+
+/* eslint-env mozilla/process-script */
+
+"use strict";
+
+/*
+ * Process script that listens for requests to start a `DevToolsServer` for an entire
+ * content process.  Loaded into content processes by the main process during
+ * content-process-connector.js' `connectToContentProcess`.
+ *
+ * The actual server startup itself is in a JSM so that code can be cached.
+ */
+
+function onInit(message) {
+  // Only reply if we are in a real content process
+  if (Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT) {
+    const { initContentProcessTarget } = ChromeUtils.importESModule(
+      "resource://devtools/server/startup/content-process.sys.mjs"
+    );
+    initContentProcessTarget(message);
+  }
+}
+
+function onClose() {
+  removeMessageListener("debug:init-content-server", onInit);
+  removeMessageListener("debug:close-content-server", onClose);
+}
+
+addMessageListener("debug:init-content-server", onInit);
+addMessageListener("debug:close-content-server", onClose);
diff --git a/devtools/server/startup/content-process.sys.mjs b/devtools/server/startup/content-process.sys.mjs
new file mode 100644
index 0000000000..fd974e8c4a
--- /dev/null
+++ b/devtools/server/startup/content-process.sys.mjs
@@ -0,0 +1,104 @@
+/* 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/. */
+
+/*
+ * Module that listens for requests to start a `DevToolsServer` for an entire content
+ * process.  Loaded into content processes by the main process during
+ * content-process-connector.js' `connectToContentProcess` via the process
+ * script `content-process.js`.
+ *
+ * The actual server startup itself is in this JSM so that code can be cached.
+ */
+
+export function initContentProcessTarget(msg) {
+  const mm = msg.target;
+  const prefix = msg.data.prefix;
+  const watcherActorID = msg.data.watcherActorID;
+
+  // Lazy load Loader.sys.mjs to prevent loading any devtools dependency too early.
+  const {
+    useDistinctSystemPrincipalLoader,
+    releaseDistinctSystemPrincipalLoader,
+  } = ChromeUtils.importESModule(
+    "resource://devtools/shared/loader/DistinctSystemPrincipalLoader.sys.mjs"
+  );
+
+  // Use a unique object to identify this one usage of the loader
+  const loaderRequester = {};
+
+  // Init a custom, invisible DevToolsServer, in order to not pollute the
+  // debugger with all devtools modules, nor break the debugger itself with
+  // using it in the same process.
+  const loader = useDistinctSystemPrincipalLoader(loaderRequester);
+
+  const { DevToolsServer } = loader.require(
+    "resource://devtools/server/devtools-server.js"
+  );
+
+  DevToolsServer.init();
+  // For browser content toolbox, we do need a regular root actor and all tab
+  // actors, but don't need all the "browser actors" that are only useful when
+  // debugging the parent process via the browser toolbox.
+  DevToolsServer.registerActors({ root: true, target: true });
+
+  // Connect both parent/child processes devtools servers RDP via message
+  // managers
+  const conn = DevToolsServer.connectToParent(prefix, mm);
+
+  const { ContentProcessTargetActor } = loader.require(
+    "resource://devtools/server/actors/targets/content-process.js"
+  );
+
+  const actor = new ContentProcessTargetActor(conn, {
+    sessionContext: msg.data.sessionContext,
+  });
+  actor.manage(actor);
+
+  const response = { watcherActorID, prefix, actor: actor.form() };
+  mm.sendAsyncMessage("debug:content-process-actor", response);
+
+  function onDestroy(options) {
+    mm.removeMessageListener(
+      "debug:content-process-disconnect",
+      onContentProcessDisconnect
+    );
+    actor.off("destroyed", onDestroy);
+
+    // Notify the parent process that the actor is being destroyed
+    mm.sendAsyncMessage("debug:content-process-actor-destroyed", {
+      watcherActorID,
+    });
+
+    // Call DevToolsServerConnection.close to destroy all child actors. It should end up
+    // calling DevToolsServerConnection.onTransportClosed that would actually cleanup all actor
+    // pools.
+    conn.close(options);
+
+    // Destroy the related loader when the target is destroyed
+    // and we were the last user of the special loader
+    releaseDistinctSystemPrincipalLoader(loaderRequester);
+  }
+  function onContentProcessDisconnect(message) {
+    if (message.data.prefix != prefix) {
+      // Several copies of this process script can be running for a single process if
+      // we are debugging the same process from multiple clients.
+      // If this disconnect request doesn't match a connection known here, ignore it.
+      return;
+    }
+    onDestroy();
+  }
+
+  // Clean up things when the client disconnects
+  mm.addMessageListener(
+    "debug:content-process-disconnect",
+    onContentProcessDisconnect
+  );
+  // And also when the target actor is destroyed
+  actor.on("destroyed", onDestroy);
+
+  return {
+    actor,
+    connection: conn,
+  };
+}
diff --git a/devtools/server/startup/frame.js b/devtools/server/startup/frame.js
new file mode 100644
index 0000000000..db14f03c15
--- /dev/null
+++ b/devtools/server/startup/frame.js
@@ -0,0 +1,193 @@
+/* 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/. */
+
+/* eslint-env mozilla/frame-script */
+
+"use strict";
+
+/* global addEventListener */
+
+/*
+ * Frame script that listens for requests to start a `DevToolsServer` for a frame in a
+ * content process.  Loaded into content process frames by the main process during
+ * frame-connector.js' connectToFrame.
+ */
+
+try {
+  var chromeGlobal = this;
+
+  // Encapsulate in its own scope to allows loading this frame script more than once.
+  (function () {
+    // In most cases, we are debugging a tab in content process, without chrome
+    // privileges. But in some tests, we are attaching to privileged document.
+    // Because the debugger can't be running in the same compartment than its debuggee,
+    // we have to load the server in a dedicated Loader, flagged with
+    // invisibleToDebugger, which will force it to be loaded in another compartment.
+    let loader,
+      customLoader = false;
+    if (content.document.nodePrincipal.isSystemPrincipal) {
+      const { useDistinctSystemPrincipalLoader } = ChromeUtils.importESModule(
+        "resource://devtools/shared/loader/DistinctSystemPrincipalLoader.sys.mjs"
+      );
+      loader = useDistinctSystemPrincipalLoader(chromeGlobal);
+      customLoader = true;
+    } else {
+      // Otherwise, use the shared loader.
+      loader = ChromeUtils.importESModule(
+        "resource://devtools/shared/loader/Loader.sys.mjs"
+      );
+    }
+    const { require } = loader;
+
+    const DevToolsUtils = require("resource://devtools/shared/DevToolsUtils.js");
+    const {
+      DevToolsServer,
+    } = require("resource://devtools/server/devtools-server.js");
+
+    DevToolsServer.init();
+    // We want a special server without any root actor and only target-scoped actors.
+    // We are going to spawn a WindowGlobalTargetActor instance in the next few lines,
+    // it is going to act like a root actor without being one.
+    DevToolsServer.registerActors({ target: true });
+
+    const connections = new Map();
+
+    const onConnect = DevToolsUtils.makeInfallible(function (msg) {
+      const mm = msg.target;
+      const prefix = msg.data.prefix;
+      const addonId = msg.data.addonId;
+      const addonBrowsingContextGroupId = msg.data.addonBrowsingContextGroupId;
+
+      // If we try to create several frame targets simultaneously, the frame script will be loaded several times.
+      // In this case a single "debug:connect" message might be received by all the already loaded frame scripts.
+      // Check if the DevToolsServer already knows the provided connection prefix,
+      // because it means that another framescript instance already handled this message.
+      // Another "debug:connect" message is guaranteed to be emitted for another prefix,
+      // so we keep the message listener and wait for this next message.
+      if (DevToolsServer.hasConnectionForPrefix(prefix)) {
+        return;
+      }
+      removeMessageListener("debug:connect", onConnect);
+
+      const conn = DevToolsServer.connectToParent(prefix, mm);
+      connections.set(prefix, conn);
+
+      let actor;
+
+      if (addonId) {
+        const {
+          WebExtensionTargetActor,
+        } = require("resource://devtools/server/actors/targets/webextension.js");
+        const {
+          createWebExtensionSessionContext,
+        } = require("resource://devtools/server/actors/watcher/session-context.js");
+        const { browsingContext } = docShell;
+        actor = new WebExtensionTargetActor(conn, {
+          addonId,
+          addonBrowsingContextGroupId,
+          chromeGlobal,
+          isTopLevelTarget: true,
+          prefix,
+          sessionContext: createWebExtensionSessionContext(
+            {
+              addonId,
+              browsingContextID: browsingContext.id,
+              innerWindowId: browsingContext.currentWindowContext.innerWindowId,
+            },
+            {
+              isServerTargetSwitchingEnabled:
+                msg.data.isServerTargetSwitchingEnabled,
+            }
+          ),
+        });
+      } else {
+        const {
+          WindowGlobalTargetActor,
+        } = require("resource://devtools/server/actors/targets/window-global.js");
+        const {
+          createBrowserElementSessionContext,
+        } = require("resource://devtools/server/actors/watcher/session-context.js");
+
+        const { docShell } = chromeGlobal;
+        // For a script loaded via loadFrameScript, the global is the content
+        // message manager.
+        // All WindowGlobalTarget actors created via the framescript are top-level
+        // targets. Non top-level WindowGlobalTarget actors are all created by the
+        // DevToolsFrameChild actor.
+        //
+        // createBrowserElementSessionContext only reads browserId attribute
+        const fakeBrowserElement = {
+          browserId: docShell.browsingContext.browserId,
+        };
+        actor = new WindowGlobalTargetActor(conn, {
+          docShell,
+          isTopLevelTarget: true,
+          // This is only used when server target switching is off and we create
+          // the target from TabDescriptor. So all config attributes are false.
+          sessionContext: createBrowserElementSessionContext(
+            fakeBrowserElement,
+            {}
+          ),
+        });
+      }
+      actor.manage(actor);
+
+      sendAsyncMessage("debug:actor", { actor: actor.form(), prefix });
+    });
+
+    addMessageListener("debug:connect", onConnect);
+
+    const onDisconnect = DevToolsUtils.makeInfallible(function (msg) {
+      const prefix = msg.data.prefix;
+      const conn = connections.get(prefix);
+      if (!conn) {
+        // Several copies of this frame script can be running for a single frame since it
+        // is loaded once for each DevTools connection to the frame.  If this disconnect
+        // request doesn't match a connection known here, ignore it.
+        return;
+      }
+
+      removeMessageListener("debug:disconnect", onDisconnect);
+      // Call DevToolsServerConnection.close to destroy all child actors. It should end up
+      // calling DevToolsServerConnection.onTransportClosed that would actually cleanup all actor
+      // pools.
+      conn.close();
+      connections.delete(prefix);
+    });
+    addMessageListener("debug:disconnect", onDisconnect);
+
+    // In non-e10s mode, the "debug:disconnect" message isn't always received before the
+    // messageManager connection goes away.  Watching for "unload" here ensures we close
+    // any connections when the frame is unloaded.
+    addEventListener("unload", () => {
+      for (const conn of connections.values()) {
+        conn.close();
+      }
+      connections.clear();
+    });
+
+    // Destroy the server once its last connection closes. Note that multiple frame
+    // scripts may be running in parallel and reuse the same server.
+    function destroyLoader() {
+      // Only destroy the server if there is no more connections to it. It may be used
+      // to debug another tab running in the same process.
+      if (DevToolsServer.hasConnection() || DevToolsServer.keepAlive) {
+        return;
+      }
+      DevToolsServer.off("connectionchange", destroyLoader);
+
+      // When debugging chrome pages, we initialized a dedicated loader, also destroy it
+      if (customLoader) {
+        const { releaseDistinctSystemPrincipalLoader } =
+          ChromeUtils.importESModule(
+            "resource://devtools/shared/loader/DistinctSystemPrincipalLoader.sys.mjs"
+          );
+        releaseDistinctSystemPrincipalLoader(chromeGlobal);
+      }
+    }
+    DevToolsServer.on("connectionchange", destroyLoader);
+  })();
+} catch (e) {
+  dump(`Exception in DevTools frame startup: ${e}\n`);
+}
diff --git a/devtools/server/startup/moz.build b/devtools/server/startup/moz.build
new file mode 100644
index 0000000000..4237d88599
--- /dev/null
+++ b/devtools/server/startup/moz.build
@@ -0,0 +1,13 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+DevToolsModules(
+    "content-process-script.js",
+    "content-process.js",
+    "content-process.sys.mjs",
+    "frame.js",
+    "worker.js",
+)
diff --git a/devtools/server/startup/worker.js b/devtools/server/startup/worker.js
new file mode 100644
index 0000000000..0171cc7ae0
--- /dev/null
+++ b/devtools/server/startup/worker.js
@@ -0,0 +1,152 @@
+/* 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";
+
+/* eslint-env mozilla/chrome-worker */
+/* global worker, loadSubScript, global */
+
+/*
+ * Worker debugger script that listens for requests to start a `DevToolsServer` for a
+ * worker in a process.  Loaded into a specific worker during worker-connector.js'
+ * `connectToWorker` which is called from the same process as the worker.
+ */
+
+// This function is used to do remote procedure calls from the worker to the
+// main thread. It is exposed as a built-in global to every module by the
+// worker loader. To make sure the worker loader can access it, it needs to be
+// defined before loading the worker loader script below.
+let nextId = 0;
+this.rpc = function (method, ...params) {
+  return new Promise((resolve, reject) => {
+    const id = nextId++;
+    this.addEventListener("message", function onMessageForRpc(event) {
+      const packet = JSON.parse(event.data);
+      if (packet.type !== "rpc" || packet.id !== id) {
+        return;
+      }
+      if (packet.error) {
+        reject(packet.error);
+      } else {
+        resolve(packet.result);
+      }
+      this.removeEventListener("message", onMessageForRpc);
+    });
+
+    postMessage(
+      JSON.stringify({
+        type: "rpc",
+        method,
+        params,
+        id,
+      })
+    );
+  });
+}.bind(this);
+
+loadSubScript("resource://devtools/shared/loader/worker-loader.js");
+
+const { WorkerTargetActor } = worker.require(
+  "resource://devtools/server/actors/targets/worker.js"
+);
+const { DevToolsServer } = worker.require(
+  "resource://devtools/server/devtools-server.js"
+);
+
+DevToolsServer.createRootActor = function () {
+  throw new Error("Should never get here!");
+};
+
+// This file is only instanciated once for a given WorkerDebugger, which means that
+// multiple toolbox could end up using the same instance of this script. In order to handle
+// that, we handle a Map of the different connections, keyed by forwarding prefix.
+const connections = new Map();
+
+this.addEventListener("message", async function (event) {
+  const packet = JSON.parse(event.data);
+  switch (packet.type) {
+    case "connect":
+      const { forwardingPrefix } = packet;
+
+      // Force initializing the server each time on connect
+      // as it may have been destroyed by a previous, now closed toolbox.
+      // Once the last connection drops, the server auto destroy itself.
+      DevToolsServer.init();
+
+      // Step 3: Create a connection to the parent.
+      const connection = DevToolsServer.connectToParent(forwardingPrefix, this);
+
+      // Step 4: Create a WorkerTarget actor.
+      const workerTargetActor = new WorkerTargetActor(
+        connection,
+        global,
+        packet.workerDebuggerData,
+        packet.options.sessionContext
+      );
+      // Make the worker manage itself so it is put in a Pool and assigned an actorID.
+      workerTargetActor.manage(workerTargetActor);
+
+      workerTargetActor.on(
+        "worker-thread-attached",
+        function onThreadAttached() {
+          postMessage(JSON.stringify({ type: "worker-thread-attached" }));
+        }
+      );
+
+      // Step 5: Send a response packet to the parent to notify
+      // it that a connection has been established.
+      connections.set(forwardingPrefix, {
+        connection,
+        workerTargetActor,
+      });
+
+      postMessage(
+        JSON.stringify({
+          type: "connected",
+          forwardingPrefix,
+          workerTargetForm: workerTargetActor.form(),
+        })
+      );
+
+      // We might receive data to watch.
+      if (packet.options.sessionData) {
+        const promises = [];
+        for (const [type, entries] of Object.entries(
+          packet.options.sessionData
+        )) {
+          promises.push(workerTargetActor.addSessionDataEntry(type, entries));
+        }
+        await Promise.all(promises);
+      }
+
+      break;
+
+    case "add-session-data-entry":
+      await connections
+        .get(packet.forwardingPrefix)
+        .workerTargetActor.addSessionDataEntry(
+          packet.dataEntryType,
+          packet.entries
+        );
+      postMessage(JSON.stringify({ type: "session-data-entry-added" }));
+      break;
+
+    case "remove-session-data-entry":
+      await connections
+        .get(packet.forwardingPrefix)
+        .workerTargetActor.removeSessionDataEntry(
+          packet.dataEntryType,
+          packet.entries
+        );
+      break;
+
+    case "disconnect":
+      // This will destroy the associate WorkerTargetActor (and the actors it manages).
+      if (connections.has(packet.forwardingPrefix)) {
+        connections.get(packet.forwardingPrefix).connection.close();
+        connections.delete(packet.forwardingPrefix);
+      }
+      break;
+  }
+});