diff -r 000000000000 -r 6474c204b198 dom/apps/src/AppsServiceChild.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/apps/src/AppsServiceChild.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,122 @@
+/* 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 Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+// This module exposes a subset of the functionnalities of the parent DOM
+// Registry to content processes, to be be used from the AppsService component.
+
+this.EXPORTED_SYMBOLS = ["DOMApplicationRegistry"];
+
+Cu.import("resource://gre/modules/AppsUtils.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+
+function debug(s) {
+  //dump("-*- AppsServiceChild.jsm: " + s + "\n");
+}
+
+this.DOMApplicationRegistry = {
+  init: function init() {
+    debug("init");
+    this.cpmm = Cc["@mozilla.org/childprocessmessagemanager;1"]
+                  .getService(Ci.nsISyncMessageSender);
+
+    ["Webapps:AddApp", "Webapps:RemoveApp"].forEach((function(aMsgName) {
+      this.cpmm.addMessageListener(aMsgName, this);
+    }).bind(this));
+
+    // We need to prime the cache with the list of apps.
+    // XXX shoud we do this async and block callers if it's not yet there?
+    this.webapps = this.cpmm.sendSyncMessage("Webapps:GetList", { })[0];
+
+    // We need a fast mapping from localId -> app, so we add an index.
+    this.localIdIndex = { };
+    for (let id in this.webapps) {
+      let app = this.webapps[id];
+      this.localIdIndex[app.localId] = app;
+    }
+
+    Services.obs.addObserver(this, "xpcom-shutdown", false);
+  },
+
+  observe: function(aSubject, aTopic, aData) {
+    // cpmm.addMessageListener causes the DOMApplicationRegistry object to live
+    // forever if we don't clean up properly.
+    this.webapps = null;
+    ["Webapps:AddApp", "Webapps:RemoveApp"].forEach((function(aMsgName) {
+      this.cpmm.removeMessageListener(aMsgName, this);
+    }).bind(this));
+  },
+
+  receiveMessage: function receiveMessage(aMessage) {
+    debug("Received " + aMessage.name + " message.");
+    let msg = aMessage.json;
+    switch (aMessage.name) {
+      case "Webapps:AddApp":
+        this.webapps[msg.id] = msg.app;
+        this.localIdIndex[msg.app.localId] = msg.app;
+        break;
+      case "Webapps:RemoveApp":
+        delete this.localIdIndex[this.webapps[msg.id].localId];
+        delete this.webapps[msg.id];
+        break;
+    }
+  },
+
+  getAppByManifestURL: function getAppByManifestURL(aManifestURL) {
+    debug("getAppByManifestURL " + aManifestURL);
+    return AppsUtils.getAppByManifestURL(this.webapps, aManifestURL);
+  },
+
+  getAppLocalIdByManifestURL: function getAppLocalIdByManifestURL(aManifestURL) {
+    debug("getAppLocalIdByManifestURL " + aManifestURL);
+    return AppsUtils.getAppLocalIdByManifestURL(this.webapps, aManifestURL);
+  },
+
+  getCSPByLocalId: function(aLocalId) {
+    debug("getCSPByLocalId:" + aLocalId);
+    return AppsUtils.getCSPByLocalId(this.webapps, aLocalId);
+  },
+
+  getAppLocalIdByStoreId: function(aStoreId) {
+    debug("getAppLocalIdByStoreId:" + aStoreId);
+    return AppsUtils.getAppLocalIdByStoreId(this.webapps, aStoreId);
+  },
+
+  getAppByLocalId: function getAppByLocalId(aLocalId) {
+    debug("getAppByLocalId " + aLocalId);
+    let app = this.localIdIndex[aLocalId];
+    if (!app) {
+      debug("Ouch, No app!");
+      return null;
+    }
+
+    return new mozIApplication(app);
+  },
+
+  getManifestURLByLocalId: function getManifestURLByLocalId(aLocalId) {
+    debug("getManifestURLByLocalId " + aLocalId);
+    return AppsUtils.getManifestURLByLocalId(this.webapps, aLocalId);
+  },
+
+  getCoreAppsBasePath: function getCoreAppsBasePath() {
+    debug("getCoreAppsBasePath() not yet supported on child!");
+    return null;
+  },
+
+  getWebAppsBasePath: function getWebAppsBasePath() {
+    debug("getWebAppsBasePath() not yet supported on child!");
+    return null;
+  },
+
+  getAppInfo: function getAppInfo(aAppId) {
+    return AppsUtils.getAppInfo(this.webapps, aAppId);
+  }
+}
+
+DOMApplicationRegistry.init();