Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

7 files changed, 882 insertions, 0 deletions

diff --git a/devtools/client/fronts/descriptors/descriptor-mixin.js b/devtools/client/fronts/descriptors/descriptor-mixin.js
new file mode 100644
index 0000000000..ac38e104b5
--- /dev/null
+++ b/devtools/client/fronts/descriptors/descriptor-mixin.js
@@ -0,0 +1,60 @@
+/* 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";
+
+/**
+ * A Descriptor represents a debuggable context. It can be a browser tab, a tab on
+ * a remote device, like a tab on Firefox for Android. But it can also be an add-on,
+ * as well as firefox parent process, or just one of its content process.
+ * It can be very similar to a Target. The key difference is the lifecycle of these two classes.
+ * The descriptor is meant to be always alive and meaningful/usable until the end of the RDP connection.
+ * Typically a Tab Descriptor will describe the tab and not the one document currently loaded in this tab,
+ * while the Target, will describe this one document and a new Target may be created on each navigation.
+ */
+function DescriptorMixin(parentClass) {
+  class Descriptor extends parentClass {
+    constructor(client, targetFront, parentFront) {
+      super(client, targetFront, parentFront);
+
+      this._client = client;
+
+      // Pass a true value in order to distinguish this event reception
+      // from any manual destroy caused by the frontend
+      this.on(
+        "descriptor-destroyed",
+        this.destroy.bind(this, { isServerDestroyEvent: true })
+      );
+    }
+
+    get client() {
+      return this._client;
+    }
+
+    async destroy({ isServerDestroyEvent } = {}) {
+      if (this.isDestroyed()) {
+        return;
+      }
+      // This workaround is mostly done for Workers, as WorkerDescriptor
+      // extends the Target class, which causes some issue down the road:
+      // In Target.destroy, we call WorkerDescriptorActor.detach *before* calling super.destroy(),
+      // and so hold on before calling Front.destroy() which would reject all pending requests, including detach().
+      // When calling detach, the server will emit "descriptor-destroyed", which will call Target.destroy again,
+      // but will still be blocked on detach resolution and won't call Front.destroy, and won't reject pending requests either.
+      //
+      // So call Front.baseFrontClassDestroyed manually from here, so that we ensure rejecting the pending detach request
+      // and unblock Target.destroy resolution.
+      //
+      // Here is the inheritance chain for WorkerDescriptor:
+      // WorkerDescriptor -> Descriptor (from descriptor-mixin.js) -> Target (from target-mixin.js) -> Front (protocol.js) -> Pool (protocol.js) -> EventEmitter
+      if (isServerDestroyEvent) {
+        this.baseFrontClassDestroy();
+      }
+
+      await super.destroy();
+    }
+  }
+  return Descriptor;
+}
+exports.DescriptorMixin = DescriptorMixin;
diff --git a/devtools/client/fronts/descriptors/descriptor-types.js b/devtools/client/fronts/descriptors/descriptor-types.js
new file mode 100644
index 0000000000..00164509ab
--- /dev/null
+++ b/devtools/client/fronts/descriptors/descriptor-types.js
@@ -0,0 +1,17 @@
+/* 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";
+
+/**
+ * List of all descriptor types.
+ *
+ * This will be expose via `descriptorType` on all descriptor fronts.
+ */
+module.exports = {
+  PROCESS: "process",
+  WORKER: "worker",
+  TAB: "tab",
+  EXTENSION: "extension",
+};
diff --git a/devtools/client/fronts/descriptors/moz.build b/devtools/client/fronts/descriptors/moz.build
new file mode 100644
index 0000000000..665a0f252a
--- /dev/null
+++ b/devtools/client/fronts/descriptors/moz.build
@@ -0,0 +1,14 @@
+# -*- 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(
+    "descriptor-mixin.js",
+    "descriptor-types.js",
+    "process.js",
+    "tab.js",
+    "webextension.js",
+    "worker.js",
+)
diff --git a/devtools/client/fronts/descriptors/process.js b/devtools/client/fronts/descriptors/process.js
new file mode 100644
index 0000000000..6efc1bd4d7
--- /dev/null
+++ b/devtools/client/fronts/descriptors/process.js
@@ -0,0 +1,142 @@
+/* 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 {
+  processDescriptorSpec,
+} = require("resource://devtools/shared/specs/descriptors/process.js");
+const {
+  WindowGlobalTargetFront,
+} = require("resource://devtools/client/fronts/targets/window-global.js");
+const {
+  ContentProcessTargetFront,
+} = require("resource://devtools/client/fronts/targets/content-process.js");
+const {
+  FrontClassWithSpec,
+  registerFront,
+} = require("resource://devtools/shared/protocol.js");
+const {
+  DescriptorMixin,
+} = require("resource://devtools/client/fronts/descriptors/descriptor-mixin.js");
+const DESCRIPTOR_TYPES = require("resource://devtools/client/fronts/descriptors/descriptor-types.js");
+
+class ProcessDescriptorFront extends DescriptorMixin(
+  FrontClassWithSpec(processDescriptorSpec)
+) {
+  constructor(client, targetFront, parentFront) {
+    super(client, targetFront, parentFront);
+    this._isParent = false;
+    this._processTargetFront = null;
+    this._targetFrontPromise = null;
+  }
+
+  descriptorType = DESCRIPTOR_TYPES.PROCESS;
+
+  form(json) {
+    this.id = json.id;
+    this._isParent = json.isParent;
+    this._isWindowlessParent = json.isWindowlessParent;
+    this.traits = json.traits || {};
+  }
+
+  async _createProcessTargetFront(form) {
+    let front = null;
+    // the request to getTarget may return a ContentProcessTargetActor or a
+    // ParentProcessTargetActor. In most cases getProcess(0) will return the
+    // main process target actor, which is a ParentProcessTargetActor, but
+    // not in xpcshell, which uses a ContentProcessTargetActor. So select
+    // the right front based on the actor ID.
+    if (form.actor.includes("parentProcessTarget")) {
+      // ParentProcessTargetActor doesn't have a specific front, instead it uses
+      // WindowGlobalTargetFront on the client side.
+      front = new WindowGlobalTargetFront(this._client, null, this);
+    } else {
+      front = new ContentProcessTargetFront(this._client, null, this);
+    }
+    // As these fronts aren't instantiated by protocol.js, we have to set their actor ID
+    // manually like that:
+    front.actorID = form.actor;
+    front.form(form);
+
+    // @backward-compat { version 84 } Older server don't send the processID in the form
+    if (!front.processID) {
+      front.processID = this.id;
+    }
+
+    this.manage(front);
+    return front;
+  }
+
+  /**
+   * This flag should be true for parent process descriptors of a regular
+   * browser instance, where you can expect the target to be associated with a
+   * window global.
+   *
+   * This will typically be true for the descriptor used by the Browser Toolbox
+   * or the Browser Console opened against a regular Firefox instance.
+   *
+   * On the contrary this will be false for parent process descriptors created
+   * for xpcshell debugging or for background task debugging.
+   */
+  get isBrowserProcessDescriptor() {
+    return this._isParent && !this._isWindowlessParent;
+  }
+
+  get isParentProcessDescriptor() {
+    return this._isParent;
+  }
+
+  get isProcessDescriptor() {
+    return true;
+  }
+
+  getCachedTarget() {
+    return this._processTargetFront;
+  }
+
+  async getTarget() {
+    // Only return the cached Target if it is still alive.
+    if (this._processTargetFront && !this._processTargetFront.isDestroyed()) {
+      return this._processTargetFront;
+    }
+    // Otherwise, ensure that we don't try to spawn more than one Target by
+    // returning the pending promise
+    if (this._targetFrontPromise) {
+      return this._targetFrontPromise;
+    }
+    this._targetFrontPromise = (async () => {
+      let targetFront = null;
+      try {
+        const targetForm = await super.getTarget();
+        targetFront = await this._createProcessTargetFront(targetForm);
+      } catch (e) {
+        // This is likely to happen if we get a lot of events which drop previous
+        // processes.
+        console.log(
+          `Request to connect to ProcessDescriptor "${this.id}" failed: ${e}`
+        );
+      }
+      // Save the reference to the target only after the call to attach
+      // so that getTarget always returns the attached target in case of concurrent calls
+      this._processTargetFront = targetFront;
+      // clear the promise if we are finished so that we can re-connect if
+      // necessary
+      this._targetFrontPromise = null;
+      return targetFront;
+    })();
+    return this._targetFrontPromise;
+  }
+
+  destroy() {
+    if (this._processTargetFront) {
+      this._processTargetFront.destroy();
+      this._processTargetFront = null;
+    }
+    this._targetFrontPromise = null;
+    super.destroy();
+  }
+}
+
+exports.ProcessDescriptorFront = ProcessDescriptorFront;
+registerFront(ProcessDescriptorFront);
diff --git a/devtools/client/fronts/descriptors/tab.js b/devtools/client/fronts/descriptors/tab.js
new file mode 100644
index 0000000000..097aed7674
--- /dev/null
+++ b/devtools/client/fronts/descriptors/tab.js
@@ -0,0 +1,330 @@
+/* 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 {
+  tabDescriptorSpec,
+} = require("resource://devtools/shared/specs/descriptors/tab.js");
+const DESCRIPTOR_TYPES = require("resource://devtools/client/fronts/descriptors/descriptor-types.js");
+
+loader.lazyRequireGetter(
+  this,
+  "gDevTools",
+  "resource://devtools/client/framework/devtools.js",
+  true
+);
+loader.lazyRequireGetter(
+  this,
+  "WindowGlobalTargetFront",
+  "resource://devtools/client/fronts/targets/window-global.js",
+  true
+);
+const {
+  FrontClassWithSpec,
+  registerFront,
+} = require("resource://devtools/shared/protocol.js");
+const {
+  DescriptorMixin,
+} = require("resource://devtools/client/fronts/descriptors/descriptor-mixin.js");
+
+const POPUP_DEBUG_PREF = "devtools.popups.debug";
+
+/**
+ * DescriptorFront for tab targets.
+ *
+ * @fires remoteness-change
+ *        Fired only for target switching, when the debugged tab is a local tab.
+ *        TODO: This event could move to the server in order to support
+ *        remoteness change for remote debugging.
+ */
+class TabDescriptorFront extends DescriptorMixin(
+  FrontClassWithSpec(tabDescriptorSpec)
+) {
+  constructor(client, targetFront, parentFront) {
+    super(client, targetFront, parentFront);
+
+    // The tab descriptor can be configured to create either local tab targets
+    // (eg, regular tab toolbox) or browsing context targets (eg tab remote
+    // debugging).
+    this._localTab = null;
+
+    // Flag to prevent the server from trying to spawn targets by the watcher actor.
+    this._disableTargetSwitching = false;
+
+    this._onTargetDestroyed = this._onTargetDestroyed.bind(this);
+    this._handleTabEvent = this._handleTabEvent.bind(this);
+
+    // When the target is created from the server side,
+    // it is not created via TabDescriptor.getTarget.
+    // Instead, it is retrieved by the TargetCommand which
+    // will call TabDescriptor.setTarget from TargetCommand.onTargetAvailable
+    if (this.isServerTargetSwitchingEnabled()) {
+      this._targetFrontPromise = new Promise(
+        r => (this._resolveTargetFrontPromise = r)
+      );
+    }
+  }
+
+  descriptorType = DESCRIPTOR_TYPES.TAB;
+
+  form(json) {
+    this.actorID = json.actor;
+    this._form = json;
+    this.traits = json.traits || {};
+  }
+
+  /**
+   * Destroy the front.
+   *
+   * @param Boolean If true, it means that we destroy the front when receiving the descriptor-destroyed
+   *                event from the server.
+   */
+  destroy({ isServerDestroyEvent = false } = {}) {
+    if (this.isDestroyed()) {
+      return;
+    }
+
+    // The descriptor may be destroyed first by the frontend.
+    // When closing the tab, the toolbox document is almost immediately removed from the DOM.
+    // The `unload` event fires and toolbox destroys itself, as well as its related client.
+    //
+    // In such case, we emit the descriptor-destroyed event
+    if (!isServerDestroyEvent) {
+      this.emit("descriptor-destroyed");
+    }
+    if (this.isLocalTab) {
+      this._teardownLocalTabListeners();
+    }
+    super.destroy();
+  }
+
+  getWatcher() {
+    const isPopupDebuggingEnabled = Services.prefs.getBoolPref(
+      POPUP_DEBUG_PREF,
+      false
+    );
+    return super.getWatcher({
+      isServerTargetSwitchingEnabled: this.isServerTargetSwitchingEnabled(),
+      isPopupDebuggingEnabled,
+    });
+  }
+
+  setLocalTab(localTab) {
+    this._localTab = localTab;
+    this._setupLocalTabListeners();
+  }
+
+  get isTabDescriptor() {
+    return true;
+  }
+
+  get isLocalTab() {
+    return !!this._localTab;
+  }
+
+  get localTab() {
+    return this._localTab;
+  }
+
+  _setupLocalTabListeners() {
+    this.localTab.addEventListener("TabClose", this._handleTabEvent);
+    this.localTab.addEventListener("TabRemotenessChange", this._handleTabEvent);
+  }
+
+  _teardownLocalTabListeners() {
+    this.localTab.removeEventListener("TabClose", this._handleTabEvent);
+    this.localTab.removeEventListener(
+      "TabRemotenessChange",
+      this._handleTabEvent
+    );
+  }
+
+  isServerTargetSwitchingEnabled() {
+    return !this._disableTargetSwitching;
+  }
+
+  /**
+   * Called by CommandsFactory, when the WebExtension codebase instantiates
+   * a commands. We have to flag the TabDescriptor for them as they don't support
+   * target switching and gets severely broken when enabling server target which
+   * introduce target switching for all navigations and reloads
+   */
+  setIsForWebExtension() {
+    this.disableTargetSwitching();
+  }
+
+  /**
+   * Method used by the WebExtension which still need to disable server side targets,
+   * and also a few xpcshell tests which are using legacy API and don't support watcher actor.
+   */
+  disableTargetSwitching() {
+    this._disableTargetSwitching = true;
+    // Delete these two attributes which have to be set early from the constructor,
+    // but we don't know yet if target switch should be disabled.
+    delete this._targetFrontPromise;
+    delete this._resolveTargetFrontPromise;
+  }
+
+  get isZombieTab() {
+    return this._form.isZombieTab;
+  }
+
+  get browserId() {
+    return this._form.browserId;
+  }
+
+  get selected() {
+    return this._form.selected;
+  }
+
+  get title() {
+    return this._form.title;
+  }
+
+  get url() {
+    return this._form.url;
+  }
+
+  get favicon() {
+    // Note: the favicon is not part of the default form() payload, it will be
+    // added in `retrieveFavicon`.
+    return this._form.favicon;
+  }
+
+  _createTabTarget(form) {
+    const front = new WindowGlobalTargetFront(this._client, null, this);
+
+    // As these fronts aren't instantiated by protocol.js, we have to set their actor ID
+    // manually like that:
+    front.actorID = form.actor;
+    front.form(form);
+    this.manage(front);
+    return front;
+  }
+
+  _onTargetDestroyed() {
+    // Clear the cached targetFront when the target is destroyed.
+    // Note that we are also checking that _targetFront has a valid actorID
+    // in getTarget, this acts as an additional security to avoid races.
+    this._targetFront = null;
+  }
+
+  /**
+   * Safely retrieves the favicon via getFavicon() and populates this._form.favicon.
+   *
+   * We could let callers explicitly retrieve the favicon instead of inserting it in the
+   * form dynamically.
+   */
+  async retrieveFavicon() {
+    try {
+      this._form.favicon = await this.getFavicon();
+    } catch (e) {
+      // We might request the data for a tab which is going to be destroyed.
+      // In this case the TargetFront will be destroyed. Otherwise log an error.
+      if (!this.isDestroyed()) {
+        console.error("Failed to retrieve the favicon for " + this.url, e);
+      }
+    }
+  }
+
+  /**
+   * Top-level targets created on the server will not be created and managed
+   * by a descriptor front. Instead they are created by the Watcher actor.
+   * On the client side we manually re-establish a link between the descriptor
+   * and the new top-level target.
+   */
+  setTarget(targetFront) {
+    // Completely ignore the previous target.
+    // We might nullify the _targetFront unexpectely due to previous target
+    // being destroyed after the new is created
+    if (this._targetFront) {
+      this._targetFront.off("target-destroyed", this._onTargetDestroyed);
+    }
+    this._targetFront = targetFront;
+
+    targetFront.on("target-destroyed", this._onTargetDestroyed);
+
+    if (this.isServerTargetSwitchingEnabled()) {
+      this._resolveTargetFrontPromise(targetFront);
+
+      // Set a new promise in order to:
+      // 1) Avoid leaking the targetFront we just resolved into the previous promise.
+      // 2) Never return an empty target from `getTarget`
+      //
+      // About the second point:
+      // There is a race condition where we call `onTargetDestroyed` (which clears `this.targetFront`)
+      // a bit before calling `setTarget`. So that `this.targetFront` could be null,
+      // while we now a new target will eventually come when calling `setTarget`.
+      // Setting a new promise will help wait for the next target while `_targetFront` is null.
+      // Note that `getTarget` first look into `_targetFront` before checking for `_targetFrontPromise`.
+      this._targetFrontPromise = new Promise(
+        r => (this._resolveTargetFrontPromise = r)
+      );
+    }
+  }
+  getCachedTarget() {
+    return this._targetFront;
+  }
+  async getTarget() {
+    if (this._targetFront && !this._targetFront.isDestroyed()) {
+      return this._targetFront;
+    }
+
+    if (this._targetFrontPromise) {
+      return this._targetFrontPromise;
+    }
+
+    this._targetFrontPromise = (async () => {
+      let newTargetFront = null;
+      try {
+        const targetForm = await super.getTarget();
+        newTargetFront = this._createTabTarget(targetForm);
+        this.setTarget(newTargetFront);
+      } catch (e) {
+        console.log(
+          `Request to connect to TabDescriptor "${this.id}" failed: ${e}`
+        );
+      }
+
+      this._targetFrontPromise = null;
+      return newTargetFront;
+    })();
+    return this._targetFrontPromise;
+  }
+
+  /**
+   * Handle tabs events.
+   */
+  async _handleTabEvent(event) {
+    switch (event.type) {
+      case "TabClose":
+        // Always destroy the toolbox opened for this local tab descriptor.
+        // When the toolbox is in a Window Host, it won't be removed from the
+        // DOM when the tab is closed.
+        const toolbox = gDevTools.getToolboxForDescriptorFront(this);
+        if (toolbox) {
+          // Toolbox.destroy will call target.destroy eventually.
+          await toolbox.destroy();
+        }
+        break;
+      case "TabRemotenessChange":
+        this._onRemotenessChange();
+        break;
+    }
+  }
+
+  /**
+   * Automatically respawn the toolbox when the tab changes between being
+   * loaded within the parent process and loaded from a content process.
+   * Process change can go in both ways.
+   */
+  async _onRemotenessChange() {
+    // In a near future, this client side code should be replaced by actor code,
+    // notifying about new tab targets.
+    this.emit("remoteness-change", this._targetFront);
+  }
+}
+
+exports.TabDescriptorFront = TabDescriptorFront;
+registerFront(TabDescriptorFront);
diff --git a/devtools/client/fronts/descriptors/webextension.js b/devtools/client/fronts/descriptors/webextension.js
new file mode 100644
index 0000000000..5db86ee5f8
--- /dev/null
+++ b/devtools/client/fronts/descriptors/webextension.js
@@ -0,0 +1,173 @@
+/* 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 {
+  webExtensionDescriptorSpec,
+} = require("resource://devtools/shared/specs/descriptors/webextension.js");
+const {
+  FrontClassWithSpec,
+  registerFront,
+} = require("resource://devtools/shared/protocol.js");
+const {
+  DescriptorMixin,
+} = require("resource://devtools/client/fronts/descriptors/descriptor-mixin.js");
+const DESCRIPTOR_TYPES = require("resource://devtools/client/fronts/descriptors/descriptor-types.js");
+loader.lazyRequireGetter(
+  this,
+  "WindowGlobalTargetFront",
+  "resource://devtools/client/fronts/targets/window-global.js",
+  true
+);
+
+class WebExtensionDescriptorFront extends DescriptorMixin(
+  FrontClassWithSpec(webExtensionDescriptorSpec)
+) {
+  constructor(client, targetFront, parentFront) {
+    super(client, targetFront, parentFront);
+    this.traits = {};
+  }
+
+  descriptorType = DESCRIPTOR_TYPES.EXTENSION;
+
+  form(json) {
+    this.actorID = json.actor;
+
+    // Do not use `form` name to avoid colliding with protocol.js's `form` method
+    this._form = json;
+    this.traits = json.traits || {};
+  }
+
+  get backgroundScriptStatus() {
+    return this._form.backgroundScriptStatus;
+  }
+
+  get debuggable() {
+    return this._form.debuggable;
+  }
+
+  get hidden() {
+    return this._form.hidden;
+  }
+
+  get iconDataURL() {
+    return this._form.iconDataURL;
+  }
+
+  get iconURL() {
+    return this._form.iconURL;
+  }
+
+  get id() {
+    return this._form.id;
+  }
+
+  get isSystem() {
+    return this._form.isSystem;
+  }
+
+  get isWebExtensionDescriptor() {
+    return true;
+  }
+
+  get isWebExtension() {
+    return this._form.isWebExtension;
+  }
+
+  get manifestURL() {
+    return this._form.manifestURL;
+  }
+
+  get name() {
+    return this._form.name;
+  }
+
+  get persistentBackgroundScript() {
+    return this._form.persistentBackgroundScript;
+  }
+
+  get temporarilyInstalled() {
+    return this._form.temporarilyInstalled;
+  }
+
+  get url() {
+    return this._form.url;
+  }
+
+  get warnings() {
+    return this._form.warnings;
+  }
+
+  isServerTargetSwitchingEnabled() {
+    // For now, we don't expose any target out of the WatcherActor.
+    // And the top level target is still manually instantiated by the descriptor.
+    // We most likely need to wait for full enabling of EFT before being able to spawn
+    // the extension target from the server side as doing this would most likely break
+    // the iframe dropdown. It would break it as spawning the targets from the server
+    // would probably mean getting rid of the usage of WindowGlobalTargetActor._setWindow
+    // and instead spawn one target per extension document.
+    // That, instead of having a unique target for all the documents.
+    return false;
+  }
+
+  getWatcher() {
+    return super.getWatcher({
+      isServerTargetSwitchingEnabled: this.isServerTargetSwitchingEnabled(),
+    });
+  }
+
+  _createWebExtensionTarget(form) {
+    const front = new WindowGlobalTargetFront(this.conn, null, this);
+    front.form(form);
+    this.manage(front);
+    return front;
+  }
+
+  /**
+   * Retrieve the WindowGlobalTargetFront representing a
+   * WebExtensionTargetActor if this addon is a webextension.
+   *
+   * WebExtensionDescriptors will be created for any type of addon type
+   * (webextension, search plugin, themes). Only webextensions can be targets.
+   * This method will throw for other addon types.
+   *
+   * TODO: We should filter out non-webextension & non-debuggable addons on the
+   * server to avoid the isWebExtension check here. See Bug 1644355.
+   */
+  async getTarget() {
+    if (!this.isWebExtension) {
+      throw new Error(
+        "Tried to create a target for an addon which is not a webextension: " +
+          this.actorID
+      );
+    }
+
+    if (this._targetFront && !this._targetFront.isDestroyed()) {
+      return this._targetFront;
+    }
+
+    if (this._targetFrontPromise) {
+      return this._targetFrontPromise;
+    }
+
+    this._targetFrontPromise = (async () => {
+      let targetFront = null;
+      try {
+        const targetForm = await super.getTarget();
+        targetFront = this._createWebExtensionTarget(targetForm);
+      } catch (e) {
+        console.log(
+          `Request to connect to WebExtensionDescriptor "${this.id}" failed: ${e}`
+        );
+      }
+      this._targetFront = targetFront;
+      this._targetFrontPromise = null;
+      return targetFront;
+    })();
+    return this._targetFrontPromise;
+  }
+}
+
+exports.WebExtensionDescriptorFront = WebExtensionDescriptorFront;
+registerFront(WebExtensionDescriptorFront);
diff --git a/devtools/client/fronts/descriptors/worker.js b/devtools/client/fronts/descriptors/worker.js
new file mode 100644
index 0000000000..47f016f15f
--- /dev/null
+++ b/devtools/client/fronts/descriptors/worker.js
@@ -0,0 +1,146 @@
+/* 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 {
+  workerDescriptorSpec,
+} = require("resource://devtools/shared/specs/descriptors/worker.js");
+const {
+  FrontClassWithSpec,
+  registerFront,
+} = require("resource://devtools/shared/protocol.js");
+const {
+  TargetMixin,
+} = require("resource://devtools/client/fronts/targets/target-mixin.js");
+const {
+  DescriptorMixin,
+} = require("resource://devtools/client/fronts/descriptors/descriptor-mixin.js");
+const DESCRIPTOR_TYPES = require("resource://devtools/client/fronts/descriptors/descriptor-types.js");
+
+class WorkerDescriptorFront extends DescriptorMixin(
+  TargetMixin(FrontClassWithSpec(workerDescriptorSpec))
+) {
+  constructor(client, targetFront, parentFront) {
+    super(client, targetFront, parentFront);
+
+    this.traits = {};
+  }
+
+  descriptorType = DESCRIPTOR_TYPES.WORKER;
+
+  form(json) {
+    this.actorID = json.actor;
+    this.id = json.id;
+
+    // Save the full form for Target class usage.
+    // Do not use `form` name to avoid colliding with protocol.js's `form` method
+    this.targetForm = json;
+    this._url = json.url;
+    this.type = json.type;
+    this.scope = json.scope;
+    this.fetch = json.fetch;
+    this.traits = json.traits;
+  }
+
+  get name() {
+    // this._url is nullified in TargetMixin#destroy.
+    if (!this.url) {
+      return null;
+    }
+
+    return this.url.split("/").pop();
+  }
+
+  get isWorkerDescriptor() {
+    return true;
+  }
+
+  get isDedicatedWorker() {
+    return this.type === Ci.nsIWorkerDebugger.TYPE_DEDICATED;
+  }
+
+  get isSharedWorker() {
+    return this.type === Ci.nsIWorkerDebugger.TYPE_SHARED;
+  }
+
+  get isServiceWorker() {
+    return this.type === Ci.nsIWorkerDebugger.TYPE_SERVICE;
+  }
+
+  // For now, WorkerDescriptor is morphed into a WorkerTarget when calling this method.
+  // Ideally, we would split this into two distinct classes.
+  async morphWorkerDescriptorIntoWorkerTarget() {
+    // temporary, will be moved once we have a target actor
+    return this.getTarget();
+  }
+
+  async getTarget() {
+    if (this._attach) {
+      return this._attach;
+    }
+
+    this._attach = (async () => {
+      if (this.isDestroyedOrBeingDestroyed()) {
+        return this;
+      }
+
+      if (this.isServiceWorker) {
+        this.registration = await this._getRegistrationIfActive();
+        if (this.registration) {
+          await this.registration.preventShutdown();
+        }
+      }
+
+      if (this.isDestroyedOrBeingDestroyed()) {
+        return this;
+      }
+
+      const workerTargetForm = await super.getTarget();
+
+      // Set the console and thread actor IDs on the form so it is accessible by TargetMixin.getFront
+      this.targetForm.consoleActor = workerTargetForm.consoleActor;
+      this.targetForm.threadActor = workerTargetForm.threadActor;
+      this.targetForm.tracerActor = workerTargetForm.tracerActor;
+
+      if (this.isDestroyedOrBeingDestroyed()) {
+        return this;
+      }
+
+      return this;
+    })();
+    return this._attach;
+  }
+
+  async detach() {
+    try {
+      await super.detach();
+
+      if (this.registration) {
+        // Bug 1644772 - Sometimes, the Browser Toolbox fails opening with a connection timeout
+        // with an exception related to this call to allowShutdown and its usage of detachDebugger API.
+        await this.registration.allowShutdown();
+        this.registration = null;
+      }
+    } catch (e) {
+      this.logDetachError(e, "worker");
+    }
+  }
+
+  async _getRegistrationIfActive() {
+    const { registrations } =
+      await this.client.mainRoot.listServiceWorkerRegistrations();
+    return registrations.find(({ activeWorker }) => {
+      return activeWorker && this.id === activeWorker.id;
+    });
+  }
+
+  reconfigure() {
+    // Toolbox and options panel are calling this method but Worker Target can't be
+    // reconfigured. So we ignore this call here.
+    return Promise.resolve();
+  }
+}
+
+exports.WorkerDescriptorFront = WorkerDescriptorFront;
+registerFront(exports.WorkerDescriptorFront);