diff -r 000000000000 -r 6474c204b198 b2g/components/ContentHandler.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/b2g/components/ContentHandler.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,145 @@
+/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
+
+"use strict";
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+
+XPCOMUtils.defineLazyGetter(this, "cpmm", function() {
+  return Cc["@mozilla.org/childprocessmessagemanager;1"]
+           .getService(Ci.nsIMessageSender);
+});
+
+function debug(aMsg) {
+  //dump("--*-- ContentHandler: " + aMsg + "\n");
+}
+
+const NS_ERROR_WONT_HANDLE_CONTENT = 0x805d0001;
+
+let ActivityContentFactory = {
+  createInstance: function createInstance(outer, iid) {
+    if (outer != null) {
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    }
+    return new ActivityContentHandler().QueryInterface(iid);
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIFactory])
+}
+
+function ActivityContentHandler() {
+}
+
+ActivityContentHandler.prototype = {
+  handleContent: function handleContent(aMimetype, aContext, aRequest) {
+    if (!(aRequest instanceof Ci.nsIChannel))
+      throw NS_ERROR_WONT_HANDLE_CONTENT;
+
+    let detail = {
+      "type": aMimetype,
+      "url": aRequest.URI.spec
+    };
+    cpmm.sendAsyncMessage("content-handler", detail);
+
+    aRequest.cancel(Cr.NS_BINDING_ABORTED);
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIContentHandler])
+}
+
+function ContentHandler() {
+  this.classIdMap = {};
+}
+
+ContentHandler.prototype = {
+  observe: function(aSubject, aTopic, aData) {
+    if (aTopic == "app-startup") {
+      // We only want to register these from content processes.
+      let appInfo = Cc["@mozilla.org/xre/app-info;1"];
+      if (appInfo.getService(Ci.nsIXULRuntime)
+          .processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT) {
+        return;
+      }
+    }
+
+    cpmm.addMessageListener("Activities:RegisterContentTypes", this);
+    cpmm.addMessageListener("Activities:UnregisterContentTypes", this);
+    cpmm.sendAsyncMessage("Activities:GetContentTypes", { });
+  },
+
+  /**
+    * Do the component registration for a content type.
+    * We only need to register one component per content type, even if several
+    * apps provide it, so we keep track of the number of providers for each
+    * content type.
+    */
+  registerContentHandler: function registerContentHandler(aContentType) {
+    debug("Registering " + aContentType);
+
+    // We already have a provider for this content type, just increase the
+    // tracking count.
+    if (this.classIdMap[aContentType]) {
+      this.classIdMap[aContentType].count++;
+      return;
+    }
+
+    let contractID = "@mozilla.org/uriloader/content-handler;1?type=" +
+                     aContentType;
+    let uuidGen = Cc["@mozilla.org/uuid-generator;1"]
+                    .getService(Ci.nsIUUIDGenerator);
+    let id = Components.ID(uuidGen.generateUUID().toString());
+    this.classIdMap[aContentType] = { count: 1, id: id };
+    let cr = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+    cr.registerFactory(Components.ID(id), "Activity Content Handler", contractID,
+                       ActivityContentFactory);
+  },
+
+  /**
+    * Do the component unregistration for a content type.
+    */
+  unregisterContentHandler: function registerContentHandler(aContentType) {
+    debug("Unregistering " + aContentType);
+
+    let record = this.classIdMap[aContentType];
+    if (!record) {
+      return;
+    }
+
+    // Bail out if we still have providers left for this content type.
+    if (--record.count > 0) {
+      return;
+    }
+
+    let contractID = "@mozilla.org/uriloader/content-handler;1?type=" +
+                     aContentType;
+    let cr = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+    cr.unregisterFactory(record.id, ActivityContentFactory);
+    delete this.classIdMap[aContentType]
+  },
+
+  receiveMessage: function(aMessage) {
+    let data = aMessage.data;
+
+    switch (aMessage.name) {
+      case "Activities:RegisterContentTypes":
+        data.contentTypes.forEach(this.registerContentHandler, this);
+        break;
+      case "Activities:UnregisterContentTypes":
+        data.contentTypes.forEach(this.unregisterContentHandler, this);
+        break;
+    }
+  },
+
+  classID: Components.ID("{d18d0216-d50c-11e1-ba54-efb18d0ef0ac}"),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIContentHandler,
+                                         Ci.nsIObserver,
+                                         Ci.nsISupportsWeakReference])
+};
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([ContentHandler]);