diff -r 000000000000 -r 6474c204b198 toolkit/mozapps/extensions/amContentHandler.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/mozapps/extensions/amContentHandler.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,87 @@
+/* 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 Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+
+const XPI_CONTENT_TYPE = "application/x-xpinstall";
+
+Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
+
+function amContentHandler() {
+}
+
+amContentHandler.prototype = {
+  /**
+   * Handles a new request for an application/x-xpinstall file.
+   *
+   * @param  aMimetype
+   *         The mimetype of the file
+   * @param  aContext
+   *         The context passed to nsIChannel.asyncOpen
+   * @param  aRequest
+   *         The nsIRequest dealing with the content
+   */
+  handleContent: function XCH_handleContent(aMimetype, aContext, aRequest) {
+    if (aMimetype != XPI_CONTENT_TYPE)
+      throw Cr.NS_ERROR_WONT_HANDLE_CONTENT;
+
+    if (!(aRequest instanceof Ci.nsIChannel))
+      throw Cr.NS_ERROR_WONT_HANDLE_CONTENT;
+
+    let uri = aRequest.URI;
+
+    let window = null;
+    let callbacks = aRequest.notificationCallbacks ?
+                    aRequest.notificationCallbacks :
+                    aRequest.loadGroup.notificationCallbacks;
+    if (callbacks)
+      window = callbacks.getInterface(Ci.nsIDOMWindow);
+
+    aRequest.cancel(Cr.NS_BINDING_ABORTED);
+
+    let appinfo = Cc["@mozilla.org/xre/app-info;1"].
+                  getService(Ci.nsIXULRuntime);
+    if (appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT) {
+      try {
+        if (!window.InstallTrigger) 
+          window = window.wrappedJSObject;
+  
+        if (window.InstallTrigger)
+          window.InstallTrigger.startSoftwareUpdate(uri.spec);
+        else
+          this.log("Window does not have an InstallTrigger");
+      } catch(ex) {
+        this.log(ex);
+      }
+    }
+    else {
+      let referer = null;
+      if (aRequest instanceof Ci.nsIPropertyBag2) {
+        referer = aRequest.getPropertyAsInterface("docshell.internalReferrer",
+                                                Ci.nsIURI);
+      }
+
+      let manager = Cc["@mozilla.org/addons/integration;1"].
+                    getService(Ci.amIWebInstaller);
+      manager.installAddonsFromWebpage(aMimetype, window, referer, [uri.spec],
+                                       [null], [null], [null], null, 1);
+    }
+  },
+
+  classID: Components.ID("{7beb3ba8-6ec3-41b4-b67c-da89b8518922}"),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIContentHandler]),
+
+  log : function XCH_log(aMsg) {
+    let msg = "amContentHandler.js: " + (aMsg.join ? aMsg.join("") : aMsg);
+    Cc["@mozilla.org/consoleservice;1"].getService(Ci.nsIConsoleService).
+      logStringMessage(msg);
+    dump(msg + "\n");
+  }
+};
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([amContentHandler]);