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diff --git a/toolkit/modules/WebChannel.sys.mjs b/toolkit/modules/WebChannel.sys.mjs
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+++ b/toolkit/modules/WebChannel.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/. */
+
+/**
+ * WebChannel is an abstraction that uses the Message Manager and Custom Events
+ * to create a two-way communication channel between chrome and content code.
+ */
+
+const ERRNO_UNKNOWN_ERROR = 999;
+const ERROR_UNKNOWN = "UNKNOWN_ERROR";
+
+/**
+ * WebChannelBroker is a global object that helps manage WebChannel objects.
+ * This object handles channel registration, origin validation and message multiplexing.
+ */
+
+export var WebChannelBroker = Object.create({
+  /**
+   * Register a new channel that callbacks messages
+   * based on proper origin and channel name
+   *
+   * @param channel {WebChannel}
+   */
+  registerChannel(channel) {
+    if (!this._channelMap.has(channel)) {
+      this._channelMap.set(channel);
+    } else {
+      console.error("Failed to register the channel. Channel already exists.");
+    }
+  },
+
+  /**
+   * Unregister a channel
+   *
+   * @param channelToRemove {WebChannel}
+   *        WebChannel to remove from the channel map
+   *
+   * Removes the specified channel from the channel map
+   */
+  unregisterChannel(channelToRemove) {
+    if (!this._channelMap.delete(channelToRemove)) {
+      console.error("Failed to unregister the channel. Channel not found.");
+    }
+  },
+
+  /**
+   * Object to store pairs of message origins and callback functions
+   */
+  _channelMap: new Map(),
+
+  /**
+   * Deliver a message to a registered channel.
+   *
+   * @returns bool whether we managed to find a registered channel.
+   */
+  tryToDeliver(data, sendingContext) {
+    let validChannelFound = false;
+    data.message = data.message || {};
+
+    for (var channel of this._channelMap.keys()) {
+      if (
+        channel.id === data.id &&
+        channel._originCheckCallback(sendingContext.principal)
+      ) {
+        validChannelFound = true;
+        channel.deliver(data, sendingContext);
+      }
+    }
+    return validChannelFound;
+  },
+});
+
+/**
+ * Creates a new WebChannel that listens and sends messages over some channel id
+ *
+ * @param id {String}
+ *        WebChannel id
+ * @param originOrPermission {nsIURI/string}
+ *        If an nsIURI, incoming events will be accepted from any origin matching
+ *        that URI's origin.
+ *        If a string, it names a permission, and incoming events will be accepted
+ *        from any https:// origin that has been granted that permission by the
+ *        permission manager.
+ * @constructor
+ */
+export var WebChannel = function (id, originOrPermission) {
+  if (!id || !originOrPermission) {
+    throw new Error("WebChannel id and originOrPermission are required.");
+  }
+
+  this.id = id;
+  // originOrPermission can be either an nsIURI or a string representing a
+  // permission name.
+  if (typeof originOrPermission == "string") {
+    this._originCheckCallback = requestPrincipal => {
+      // Accept events from any secure origin having the named permission.
+      // The permission manager operates on domain names rather than true
+      // origins (bug 1066517).  To mitigate that, we explicitly check that
+      // the scheme is https://.
+      let uri = Services.io.newURI(requestPrincipal.originNoSuffix);
+      if (uri.scheme != "https") {
+        return false;
+      }
+      // OK - we have https - now we can check the permission.
+      let perm = Services.perms.testExactPermissionFromPrincipal(
+        requestPrincipal,
+        originOrPermission
+      );
+      return perm == Ci.nsIPermissionManager.ALLOW_ACTION;
+    };
+  } else {
+    // Accept events from any origin matching the given URI.
+    // We deliberately use `originNoSuffix` here because we only want to
+    // restrict based on the site's origin, not on other origin attributes
+    // such as containers or private browsing.
+    this._originCheckCallback = requestPrincipal => {
+      return originOrPermission.prePath === requestPrincipal.originNoSuffix;
+    };
+  }
+  this._originOrPermission = originOrPermission;
+};
+
+WebChannel.prototype = {
+  /**
+   * WebChannel id
+   */
+  id: null,
+
+  /**
+   * The originOrPermission value passed to the constructor, mainly for
+   * debugging and tests.
+   */
+  _originOrPermission: null,
+
+  /**
+   * Callback that will be called with the principal of an incoming message
+   * to check if the request should be dispatched to the listeners.
+   */
+  _originCheckCallback: null,
+
+  /**
+   * WebChannelBroker that manages WebChannels
+   */
+  _broker: WebChannelBroker,
+
+  /**
+   * Callback that will be called with the contents of an incoming message
+   */
+  _deliverCallback: null,
+
+  /**
+   * Registers the callback for messages on this channel
+   * Registers the channel itself with the WebChannelBroker
+   *
+   * @param callback {Function}
+   *        Callback that will be called when there is a message
+   *        @param {String} id
+   *        The WebChannel id that was used for this message
+   *        @param {Object} message
+   *        The message itself
+   *        @param sendingContext {Object}
+   *        The sending context of the source of the message. Can be passed to
+   *        `send` to respond to a message.
+   *               @param sendingContext.browser {browser}
+   *                      The <browser> object that captured the
+   *                      WebChannelMessageToChrome.
+   *               @param sendingContext.eventTarget {EventTarget}
+   *                      The <EventTarget> where the message was sent.
+   *               @param sendingContext.principal {Principal}
+   *                      The <Principal> of the EventTarget where the
+   *                      message was sent.
+   */
+  listen(callback) {
+    if (this._deliverCallback) {
+      throw new Error("Failed to listen. Listener already attached.");
+    } else if (!callback) {
+      throw new Error("Failed to listen. Callback argument missing.");
+    } else {
+      this._deliverCallback = callback;
+      this._broker.registerChannel(this);
+    }
+  },
+
+  /**
+   * Resets the callback for messages on this channel
+   * Removes the channel from the WebChannelBroker
+   */
+  stopListening() {
+    this._broker.unregisterChannel(this);
+    this._deliverCallback = null;
+  },
+
+  /**
+   * Sends messages over the WebChannel id using the "WebChannelMessageToContent" event
+   *
+   * @param message {Object}
+   *        The message object that will be sent
+   * @param target {Object}
+   *        A <target> with the information of where to send the message.
+   *        @param target.browsingContext {BrowsingContext}
+   *               The browsingContext we should send the message to.
+   *        @param target.principal {Principal}
+   *               Principal of the target. Prevents messages from
+   *               being dispatched to unexpected origins. The system principal
+   *               can be specified to send to any target.
+   *        @param [target.eventTarget] {EventTarget}
+   *               Optional eventTarget within the browser, use to send to a
+   *               specific element. Can be null; if not null, should be
+   *               a ContentDOMReference.
+   */
+  send(message, target) {
+    let { browsingContext, principal, eventTarget } = target;
+
+    if (message && browsingContext && principal) {
+      let { currentWindowGlobal } = browsingContext;
+      if (!currentWindowGlobal) {
+        console.error(
+          "Failed to send a WebChannel message. No currentWindowGlobal."
+        );
+        return;
+      }
+      currentWindowGlobal
+        .getActor("WebChannel")
+        .sendAsyncMessage("WebChannelMessageToContent", {
+          id: this.id,
+          message,
+          eventTarget,
+          principal,
+        });
+    } else if (!message) {
+      console.error("Failed to send a WebChannel message. Message not set.");
+    } else {
+      console.error("Failed to send a WebChannel message. Target invalid.");
+    }
+  },
+
+  /**
+   * Deliver WebChannel messages to the set "_channelCallback"
+   *
+   * @param data {Object}
+   *        Message data
+   * @param sendingContext {Object}
+   *        Message sending context.
+   *        @param sendingContext.browsingContext {BrowsingContext}
+   *               The browsingcontext from which the
+   *               WebChannelMessageToChrome was sent.
+   *        @param sendingContext.eventTarget {EventTarget}
+   *               The <EventTarget> where the message was sent.
+   *               Can be null; if not null, should be a ContentDOMReference.
+   *        @param sendingContext.principal {Principal}
+   *               The <Principal> of the EventTarget where the message was sent.
+   *
+   */
+  deliver(data, sendingContext) {
+    if (this._deliverCallback) {
+      try {
+        this._deliverCallback(data.id, data.message, sendingContext);
+      } catch (ex) {
+        this.send(
+          {
+            errno: ERRNO_UNKNOWN_ERROR,
+            error: ex.message ? ex.message : ERROR_UNKNOWN,
+          },
+          sendingContext
+        );
+        console.error("Failed to execute WebChannel callback:");
+        console.error(ex);
+      }
+    } else {
+      console.error("No callback set for this channel.");
+    }
+  },
+};