Add m-esr52 at 52.6.0

37 files changed, 4238 insertions, 0 deletions

diff --git a/browser/components/feeds/BrowserFeeds.manifest b/browser/components/feeds/BrowserFeeds.manifest
new file mode 100644
index 000000000..ac5c299fa
--- /dev/null
+++ b/browser/components/feeds/BrowserFeeds.manifest
@@ -0,0 +1,25 @@
+# This component must restrict its registration for the app-startup category
+# to the specific list of apps that use it so it doesn't get loaded in xpcshell.
+# Thus we restrict it to these apps:
+#
+#   b2g:            {3c2e2abc-06d4-11e1-ac3b-374f68613e61}
+#   browser:        {ec8030f7-c20a-464f-9b0e-13a3a9e97384}
+#   mobile/android: {aa3c5121-dab2-40e2-81ca-7ea25febc110}
+#   mobile/xul:     {a23983c0-fd0e-11dc-95ff-0800200c9a66}
+#   graphene:       {d1bfe7d9-c01e-4237-998b-7b5f960a4314}
+
+component {229fa115-9412-4d32-baf3-2fc407f76fb1} FeedConverter.js
+contract @mozilla.org/streamconv;1?from=application/vnd.mozilla.maybe.feed&to=*/* {229fa115-9412-4d32-baf3-2fc407f76fb1}
+contract @mozilla.org/streamconv;1?from=application/vnd.mozilla.maybe.video.feed&to=*/* {229fa115-9412-4d32-baf3-2fc407f76fb1}
+contract @mozilla.org/streamconv;1?from=application/vnd.mozilla.maybe.audio.feed&to=*/* {229fa115-9412-4d32-baf3-2fc407f76fb1}
+component {2376201c-bbc6-472f-9b62-7548040a61c6} FeedConverter.js
+contract @mozilla.org/browser/feeds/result-service;1 {2376201c-bbc6-472f-9b62-7548040a61c6}
+component {4f91ef2e-57ba-472e-ab7a-b4999e42d6c0} FeedConverter.js
+contract @mozilla.org/network/protocol;1?name=feed {4f91ef2e-57ba-472e-ab7a-b4999e42d6c0}
+component {1c31ed79-accd-4b94-b517-06e0c81999d5} FeedConverter.js
+contract @mozilla.org/network/protocol;1?name=pcast {1c31ed79-accd-4b94-b517-06e0c81999d5}
+component {49bb6593-3aff-4eb3-a068-2712c28bd58e} FeedWriter.js
+contract @mozilla.org/browser/feeds/result-writer;1 {49bb6593-3aff-4eb3-a068-2712c28bd58e}
+component {792a7e82-06a0-437c-af63-b2d12e808acc} WebContentConverter.js
+contract @mozilla.org/embeddor.implemented/web-content-handler-registrar;1 {792a7e82-06a0-437c-af63-b2d12e808acc}
+category app-startup WebContentConverter service,@mozilla.org/embeddor.implemented/web-content-handler-registrar;1 application={3c2e2abc-06d4-11e1-ac3b-374f68613e61} application={ec8030f7-c20a-464f-9b0e-13a3a9e97384} application={aa3c5121-dab2-40e2-81ca-7ea25febc110} application={a23983c0-fd0e-11dc-95ff-0800200c9a66} application={d1bfe7d9-c01e-4237-998b-7b5f960a4314}
diff --git a/browser/components/feeds/FeedConverter.js b/browser/components/feeds/FeedConverter.js
new file mode 100644
index 000000000..aa70620d4
--- /dev/null
+++ b/browser/components/feeds/FeedConverter.js
@@ -0,0 +1,568 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* 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/. */
+
+Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
+Components.utils.import("resource://gre/modules/debug.js");
+Components.utils.import("resource://gre/modules/Services.jsm");
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+
+function LOG(str) {
+  dump("*** " + str + "\n");
+}
+
+const FS_CONTRACTID = "@mozilla.org/browser/feeds/result-service;1";
+const FPH_CONTRACTID = "@mozilla.org/network/protocol;1?name=feed";
+const PCPH_CONTRACTID = "@mozilla.org/network/protocol;1?name=pcast";
+
+const TYPE_MAYBE_FEED = "application/vnd.mozilla.maybe.feed";
+const TYPE_MAYBE_VIDEO_FEED = "application/vnd.mozilla.maybe.video.feed";
+const TYPE_MAYBE_AUDIO_FEED = "application/vnd.mozilla.maybe.audio.feed";
+const TYPE_ANY = "*/*";
+
+const PREF_SELECTED_APP = "browser.feeds.handlers.application";
+const PREF_SELECTED_WEB = "browser.feeds.handlers.webservice";
+const PREF_SELECTED_ACTION = "browser.feeds.handler";
+const PREF_SELECTED_READER = "browser.feeds.handler.default";
+
+const PREF_VIDEO_SELECTED_APP = "browser.videoFeeds.handlers.application";
+const PREF_VIDEO_SELECTED_WEB = "browser.videoFeeds.handlers.webservice";
+const PREF_VIDEO_SELECTED_ACTION = "browser.videoFeeds.handler";
+const PREF_VIDEO_SELECTED_READER = "browser.videoFeeds.handler.default";
+
+const PREF_AUDIO_SELECTED_APP = "browser.audioFeeds.handlers.application";
+const PREF_AUDIO_SELECTED_WEB = "browser.audioFeeds.handlers.webservice";
+const PREF_AUDIO_SELECTED_ACTION = "browser.audioFeeds.handler";
+const PREF_AUDIO_SELECTED_READER = "browser.audioFeeds.handler.default";
+
+function getPrefAppForType(t) {
+  switch (t) {
+    case Ci.nsIFeed.TYPE_VIDEO:
+      return PREF_VIDEO_SELECTED_APP;
+
+    case Ci.nsIFeed.TYPE_AUDIO:
+      return PREF_AUDIO_SELECTED_APP;
+
+    default:
+      return PREF_SELECTED_APP;
+  }
+}
+
+function getPrefWebForType(t) {
+  switch (t) {
+    case Ci.nsIFeed.TYPE_VIDEO:
+      return PREF_VIDEO_SELECTED_WEB;
+
+    case Ci.nsIFeed.TYPE_AUDIO:
+      return PREF_AUDIO_SELECTED_WEB;
+
+    default:
+      return PREF_SELECTED_WEB;
+  }
+}
+
+function getPrefActionForType(t) {
+  switch (t) {
+    case Ci.nsIFeed.TYPE_VIDEO:
+      return PREF_VIDEO_SELECTED_ACTION;
+
+    case Ci.nsIFeed.TYPE_AUDIO:
+      return PREF_AUDIO_SELECTED_ACTION;
+
+    default:
+      return PREF_SELECTED_ACTION;
+  }
+}
+
+function getPrefReaderForType(t) {
+  switch (t) {
+    case Ci.nsIFeed.TYPE_VIDEO:
+      return PREF_VIDEO_SELECTED_READER;
+
+    case Ci.nsIFeed.TYPE_AUDIO:
+      return PREF_AUDIO_SELECTED_READER;
+
+    default:
+      return PREF_SELECTED_READER;
+  }
+}
+
+function safeGetCharPref(pref, defaultValue) {
+  var prefs =
+      Cc["@mozilla.org/preferences-service;1"].
+      getService(Ci.nsIPrefBranch);
+  try {
+    return prefs.getCharPref(pref);
+  }
+  catch (e) {
+  }
+  return defaultValue;
+}
+
+function FeedConverter() {
+}
+FeedConverter.prototype = {
+  classID: Components.ID("{229fa115-9412-4d32-baf3-2fc407f76fb1}"),
+
+  /**
+   * This is the downloaded text data for the feed.
+   */
+  _data: null,
+
+  /**
+   * This is the object listening to the conversion, which is ultimately the
+   * docshell for the load.
+   */
+  _listener: null,
+
+  /**
+   * Records if the feed was sniffed
+   */
+  _sniffed: false,
+
+  /**
+   * See nsIStreamConverter.idl
+   */
+  convert(sourceStream, sourceType, destinationType,
+          context) {
+    throw Cr.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  /**
+   * See nsIStreamConverter.idl
+   */
+  asyncConvertData(sourceType, destinationType,
+                   listener, context) {
+    this._listener = listener;
+  },
+
+  /**
+   * Whether or not the preview page is being forced.
+   */
+  _forcePreviewPage: false,
+
+  /**
+   * Release our references to various things once we're done using them.
+   */
+  _releaseHandles() {
+    this._listener = null;
+    this._request = null;
+    this._processor = null;
+  },
+
+  /**
+   * See nsIFeedResultListener.idl
+   */
+  handleResult(result) {
+    // Feeds come in various content types, which our feed sniffer coerces to
+    // the maybe.feed type. However, feeds are used as a transport for
+    // different data types, e.g. news/blogs (traditional feed), video/audio
+    // (podcasts) and photos (photocasts, photostreams). Each of these is
+    // different in that there's a different class of application suitable for
+    // handling feeds of that type, but without a content-type differentiation
+    // it is difficult for us to disambiguate.
+    //
+    // The other problem is that if the user specifies an auto-action handler
+    // for one feed application, the fact that the content type is shared means
+    // that all other applications will auto-load with that handler too,
+    // regardless of the content-type.
+    //
+    // This means that content-type alone is not enough to determine whether
+    // or not a feed should be auto-handled. This means that for feeds we need
+    // to always use this stream converter, even when an auto-action is
+    // specified, not the basic one provided by WebContentConverter. This
+    // converter needs to consume all of the data and parse it, and based on
+    // that determination make a judgment about type.
+    //
+    // Since there are no content types for this content, and I'm not going to
+    // invent any, the upshot is that while a user can set an auto-handler for
+    // generic feed content, the system will prevent them from setting an auto-
+    // handler for other stream types. In those cases, the user will always see
+    // the preview page and have to select a handler. We can guess and show
+    // a client handler, but will not be able to show web handlers for those
+    // types.
+    //
+    // If this is just a feed, not some kind of specialized application, then
+    // auto-handlers can be set and we should obey them.
+    try {
+      let feedService =
+          Cc["@mozilla.org/browser/feeds/result-service;1"].
+          getService(Ci.nsIFeedResultService);
+      if (!this._forcePreviewPage && result.doc) {
+        let feed = result.doc.QueryInterface(Ci.nsIFeed);
+        let handler = safeGetCharPref(getPrefActionForType(feed.type), "ask");
+
+        if (handler != "ask") {
+          if (handler == "reader")
+            handler = safeGetCharPref(getPrefReaderForType(feed.type), "bookmarks");
+          switch (handler) {
+            case "web":
+              let wccr =
+                  Cc["@mozilla.org/embeddor.implemented/web-content-handler-registrar;1"].
+                  getService(Ci.nsIWebContentConverterService);
+              if ((feed.type == Ci.nsIFeed.TYPE_FEED &&
+                   wccr.getAutoHandler(TYPE_MAYBE_FEED)) ||
+                  (feed.type == Ci.nsIFeed.TYPE_VIDEO &&
+                   wccr.getAutoHandler(TYPE_MAYBE_VIDEO_FEED)) ||
+                  (feed.type == Ci.nsIFeed.TYPE_AUDIO &&
+                   wccr.getAutoHandler(TYPE_MAYBE_AUDIO_FEED))) {
+                wccr.loadPreferredHandler(this._request);
+                return;
+              }
+              break;
+
+            default:
+              LOG("unexpected handler: " + handler);
+              // fall through -- let feed service handle error
+            case "bookmarks":
+            case "client":
+            case "default":
+              try {
+                let title = feed.title ? feed.title.plainText() : "";
+                let desc = feed.subtitle ? feed.subtitle.plainText() : "";
+                feedService.addToClientReader(result.uri.spec, title, desc, feed.type, handler);
+                return;
+              } catch (ex) { /* fallback to preview mode */ }
+          }
+        }
+      }
+
+      let ios =
+          Cc["@mozilla.org/network/io-service;1"].
+          getService(Ci.nsIIOService);
+      let chromeChannel;
+
+      // handling a redirect, hence forwarding the loadInfo from the old channel
+      // to the newchannel.
+      let oldChannel = this._request.QueryInterface(Ci.nsIChannel);
+      let loadInfo = oldChannel.loadInfo;
+
+      // If there was no automatic handler, or this was a podcast,
+      // photostream or some other kind of application, show the preview page
+      // if the parser returned a document.
+      if (result.doc) {
+
+        // Store the result in the result service so that the display
+        // page can access it.
+        feedService.addFeedResult(result);
+
+        // Now load the actual XUL document.
+        let aboutFeedsURI = ios.newURI("about:feeds", null, null);
+        chromeChannel = ios.newChannelFromURIWithLoadInfo(aboutFeedsURI, loadInfo);
+        chromeChannel.originalURI = result.uri;
+
+        // carry the origin attributes from the channel that loaded the feed.
+        chromeChannel.owner =
+          Services.scriptSecurityManager.createCodebasePrincipal(aboutFeedsURI,
+                                                                 loadInfo.originAttributes);
+      } else {
+        chromeChannel = ios.newChannelFromURIWithLoadInfo(result.uri, loadInfo);
+      }
+
+      chromeChannel.loadGroup = this._request.loadGroup;
+      chromeChannel.asyncOpen(this._listener, null);
+    }
+    finally {
+      this._releaseHandles();
+    }
+  },
+
+  /**
+   * See nsIStreamListener.idl
+   */
+  onDataAvailable(request, context, inputStream,
+                  sourceOffset, count) {
+    if (this._processor)
+      this._processor.onDataAvailable(request, context, inputStream,
+                                      sourceOffset, count);
+  },
+
+  /**
+   * See nsIRequestObserver.idl
+   */
+  onStartRequest(request, context) {
+    let channel = request.QueryInterface(Ci.nsIChannel);
+
+    // Check for a header that tells us there was no sniffing
+    // The value doesn't matter.
+    try {
+      let httpChannel = channel.QueryInterface(Ci.nsIHttpChannel);
+      // Make sure to check requestSucceeded before the potentially-throwing
+      // getResponseHeader.
+      if (!httpChannel.requestSucceeded) {
+        // Just give up, but don't forget to cancel the channel first!
+        request.cancel(Cr.NS_BINDING_ABORTED);
+        return;
+      }
+
+      // Note: this throws if the header is not set.
+      httpChannel.getResponseHeader("X-Moz-Is-Feed");
+    }
+    catch (ex) {
+      this._sniffed = true;
+    }
+
+    this._request = request;
+
+    // Save and reset the forced state bit early, in case there's some kind of
+    // error.
+    let feedService =
+        Cc["@mozilla.org/browser/feeds/result-service;1"].
+        getService(Ci.nsIFeedResultService);
+    this._forcePreviewPage = feedService.forcePreviewPage;
+    feedService.forcePreviewPage = false;
+
+    // Parse feed data as it comes in
+    this._processor =
+        Cc["@mozilla.org/feed-processor;1"].
+        createInstance(Ci.nsIFeedProcessor);
+    this._processor.listener = this;
+    this._processor.parseAsync(null, channel.URI);
+
+    this._processor.onStartRequest(request, context);
+  },
+
+  /**
+   * See nsIRequestObserver.idl
+   */
+  onStopRequest(request, context, status) {
+    if (this._processor)
+      this._processor.onStopRequest(request, context, status);
+  },
+
+  /**
+   * See nsISupports.idl
+   */
+  QueryInterface(iid) {
+    if (iid.equals(Ci.nsIFeedResultListener) ||
+        iid.equals(Ci.nsIStreamConverter) ||
+        iid.equals(Ci.nsIStreamListener) ||
+        iid.equals(Ci.nsIRequestObserver)||
+        iid.equals(Ci.nsISupports))
+      return this;
+    throw Cr.NS_ERROR_NO_INTERFACE;
+  },
+};
+
+/**
+ * Keeps parsed FeedResults around for use elsewhere in the UI after the stream
+ * converter completes.
+ */
+function FeedResultService() {
+}
+
+FeedResultService.prototype = {
+  classID: Components.ID("{2376201c-bbc6-472f-9b62-7548040a61c6}"),
+
+  /**
+   * A URI spec -> [nsIFeedResult] hash. We have to keep a list as the
+   * value in case the same URI is requested concurrently.
+   */
+  _results: { },
+
+  /**
+   * See nsIFeedResultService.idl
+   */
+  forcePreviewPage: false,
+
+  /**
+   * See nsIFeedResultService.idl
+   */
+  addToClientReader(spec, title, subtitle, feedType, feedReader) {
+    if (!feedReader) {
+      feedReader = "default";
+    }
+
+    let handler = safeGetCharPref(getPrefActionForType(feedType), "bookmarks");
+    if (handler == "ask" || handler == "reader")
+      handler = feedReader;
+
+    switch (handler) {
+    case "client":
+      Services.cpmm.sendAsyncMessage("FeedConverter:ExecuteClientApp",
+                                     { spec,
+                                       title,
+                                       subtitle,
+                                       feedHandler: getPrefAppForType(feedType) });
+      break;
+    case "default":
+      // Default system feed reader
+      Services.cpmm.sendAsyncMessage("FeedConverter:ExecuteClientApp",
+                                     { spec,
+                                       title,
+                                       subtitle,
+                                       feedHandler: "default" });
+      break;
+    default:
+      // "web" should have been handled elsewhere
+      LOG("unexpected handler: " + handler);
+      // fall through
+    case "bookmarks":
+      Services.cpmm.sendAsyncMessage("FeedConverter:addLiveBookmark",
+                                     { spec, title, subtitle });
+      break;
+    }
+  },
+
+  /**
+   * See nsIFeedResultService.idl
+   */
+  addFeedResult(feedResult) {
+    NS_ASSERT(feedResult.uri != null, "null URI!");
+    NS_ASSERT(feedResult.uri != null, "null feedResult!");
+    let spec = feedResult.uri.spec;
+    if (!this._results[spec])
+      this._results[spec] = [];
+    this._results[spec].push(feedResult);
+  },
+
+  /**
+   * See nsIFeedResultService.idl
+   */
+  getFeedResult(uri) {
+    NS_ASSERT(uri != null, "null URI!");
+    let resultList = this._results[uri.spec];
+    for (let result of resultList) {
+      if (result.uri == uri)
+        return result;
+    }
+    return null;
+  },
+
+  /**
+   * See nsIFeedResultService.idl
+   */
+  removeFeedResult(uri) {
+    NS_ASSERT(uri != null, "null URI!");
+    let resultList = this._results[uri.spec];
+    if (!resultList)
+      return;
+    let deletions = 0;
+    for (let i = 0; i < resultList.length; ++i) {
+      if (resultList[i].uri == uri) {
+        delete resultList[i];
+        ++deletions;
+      }
+    }
+
+    // send the holes to the end
+    resultList.sort();
+    // and trim the list
+    resultList.splice(resultList.length - deletions, deletions);
+    if (resultList.length == 0)
+      delete this._results[uri.spec];
+  },
+
+  createInstance(outer, iid) {
+    if (outer != null)
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    return this.QueryInterface(iid);
+  },
+
+  QueryInterface(iid) {
+    if (iid.equals(Ci.nsIFeedResultService) ||
+        iid.equals(Ci.nsIFactory) ||
+        iid.equals(Ci.nsISupports))
+      return this;
+    throw Cr.NS_ERROR_NOT_IMPLEMENTED;
+  },
+};
+
+/**
+ * A protocol handler that attempts to deal with the variant forms of feed:
+ * URIs that are actually either http or https.
+ */
+function GenericProtocolHandler() {
+}
+GenericProtocolHandler.prototype = {
+  _init(scheme) {
+    let ios =
+      Cc["@mozilla.org/network/io-service;1"].
+      getService(Ci.nsIIOService);
+    this._http = ios.getProtocolHandler("http");
+    this._scheme = scheme;
+  },
+
+  get scheme() {
+    return this._scheme;
+  },
+
+  get protocolFlags() {
+    let {URI_DANGEROUS_TO_LOAD, ALLOWS_PROXY_HTTP, ALLOWS_PROXY} =
+      Ci.nsIProtocolHandler;
+    return URI_DANGEROUS_TO_LOAD | ALLOWS_PROXY | ALLOWS_PROXY_HTTP;
+  },
+
+  get defaultPort() {
+    return this._http.defaultPort;
+  },
+
+  allowPort(port, scheme) {
+    return this._http.allowPort(port, scheme);
+  },
+
+  newURI(spec, originalCharset, baseURI) {
+    // Feed URIs can be either nested URIs of the form feed:realURI (in which
+    // case we create a nested URI for the realURI) or feed://example.com, in
+    // which case we create a nested URI for the real protocol which is http.
+
+    let scheme = this._scheme + ":";
+    if (spec.substr(0, scheme.length) != scheme)
+      throw Cr.NS_ERROR_MALFORMED_URI;
+
+    let prefix = spec.substr(scheme.length, 2) == "//" ? "http:" : "";
+    let inner = Services.io.newURI(spec.replace(scheme, prefix),
+                                   originalCharset, baseURI);
+
+    if (!["http", "https"].includes(inner.scheme))
+      throw Cr.NS_ERROR_MALFORMED_URI;
+
+    let uri = Services.io.QueryInterface(Ci.nsINetUtil).newSimpleNestedURI(inner);
+    uri.spec = inner.spec.replace(prefix, scheme);
+    return uri;
+  },
+
+  newChannel2(aUri, aLoadInfo) {
+    let inner = aUri.QueryInterface(Ci.nsINestedURI).innerURI;
+    let channel = Cc["@mozilla.org/network/io-service;1"].
+                  getService(Ci.nsIIOService).
+                  newChannelFromURIWithLoadInfo(inner, aLoadInfo);
+
+    if (channel instanceof Components.interfaces.nsIHttpChannel)
+      // Set this so we know this is supposed to be a feed
+      channel.setRequestHeader("X-Moz-Is-Feed", "1", false);
+    channel.originalURI = aUri;
+    return channel;
+  },
+
+  QueryInterface(iid) {
+    if (iid.equals(Ci.nsIProtocolHandler) ||
+        iid.equals(Ci.nsISupports))
+      return this;
+    throw Cr.NS_ERROR_NO_INTERFACE;
+  }
+};
+
+function FeedProtocolHandler() {
+  this._init('feed');
+}
+FeedProtocolHandler.prototype = new GenericProtocolHandler();
+FeedProtocolHandler.prototype.classID = Components.ID("{4f91ef2e-57ba-472e-ab7a-b4999e42d6c0}");
+
+function PodCastProtocolHandler() {
+  this._init('pcast');
+}
+PodCastProtocolHandler.prototype = new GenericProtocolHandler();
+PodCastProtocolHandler.prototype.classID = Components.ID("{1c31ed79-accd-4b94-b517-06e0c81999d5}");
+
+var components = [FeedConverter,
+                  FeedResultService,
+                  FeedProtocolHandler,
+                  PodCastProtocolHandler];
+
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory(components);
diff --git a/browser/components/feeds/FeedWriter.js b/browser/components/feeds/FeedWriter.js
new file mode 100644
index 000000000..20f1399b0
--- /dev/null
+++ b/browser/components/feeds/FeedWriter.js
@@ -0,0 +1,1007 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* 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/. */
+
+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");
+Cu.import("resource://gre/modules/NetUtil.jsm");
+
+const FEEDWRITER_CID = Components.ID("{49bb6593-3aff-4eb3-a068-2712c28bd58e}");
+const FEEDWRITER_CONTRACTID = "@mozilla.org/browser/feeds/result-writer;1";
+
+function LOG(str) {
+  let prefB = Cc["@mozilla.org/preferences-service;1"].
+              getService(Ci.nsIPrefBranch);
+
+  let shouldLog = false;
+  try {
+    shouldLog = prefB.getBoolPref("feeds.log");
+  }
+  catch (ex) {
+  }
+
+  if (shouldLog)
+    dump("*** Feeds: " + str + "\n");
+}
+
+/**
+ * Wrapper function for nsIIOService::newURI.
+ * @param aURLSpec
+ *        The URL string from which to create an nsIURI.
+ * @returns an nsIURI object, or null if the creation of the URI failed.
+ */
+function makeURI(aURLSpec, aCharset) {
+  let ios = Cc["@mozilla.org/network/io-service;1"].
+            getService(Ci.nsIIOService);
+  try {
+    return ios.newURI(aURLSpec, aCharset, null);
+  } catch (ex) { }
+
+  return null;
+}
+
+const XML_NS = "http://www.w3.org/XML/1998/namespace";
+const HTML_NS = "http://www.w3.org/1999/xhtml";
+const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
+const URI_BUNDLE = "chrome://browser/locale/feeds/subscribe.properties";
+
+const TITLE_ID = "feedTitleText";
+const SUBTITLE_ID = "feedSubtitleText";
+
+/**
+ * Converts a number of bytes to the appropriate unit that results in a
+ * number that needs fewer than 4 digits
+ *
+ * @return a pair: [new value with 3 sig. figs., its unit]
+  */
+function convertByteUnits(aBytes) {
+  let units = ["bytes", "kilobyte", "megabyte", "gigabyte"];
+  let unitIndex = 0;
+
+  // convert to next unit if it needs 4 digits (after rounding), but only if
+  // we know the name of the next unit
+  while ((aBytes >= 999.5) && (unitIndex < units.length - 1)) {
+    aBytes /= 1024;
+    unitIndex++;
+  }
+
+  // Get rid of insignificant bits by truncating to 1 or 0 decimal points
+  // 0 -> 0; 1.2 -> 1.2; 12.3 -> 12.3; 123.4 -> 123; 234.5 -> 235
+  aBytes = aBytes.toFixed((aBytes > 0) && (aBytes < 100) ? 1 : 0);
+
+  return [aBytes, units[unitIndex]];
+}
+
+function FeedWriter() {
+  this._selectedApp = undefined;
+  this._selectedAppMenuItem = null;
+  this._subscribeCallback = null;
+  this._defaultHandlerMenuItem = null;
+}
+
+FeedWriter.prototype = {
+  _getPropertyAsBag(container, property) {
+    return container.fields.getProperty(property).
+                     QueryInterface(Ci.nsIPropertyBag2);
+  },
+
+  _getPropertyAsString(container, property) {
+    try {
+      return container.fields.getPropertyAsAString(property);
+    }
+    catch (e) {
+    }
+    return "";
+  },
+
+  _setContentText(id, text) {
+    let element = this._document.getElementById(id);
+    let textNode = text.createDocumentFragment(element);
+    while (element.hasChildNodes())
+      element.removeChild(element.firstChild);
+    element.appendChild(textNode);
+    if (text.base) {
+      element.setAttributeNS(XML_NS, 'base', text.base.spec);
+    }
+  },
+
+  /**
+   * Safely sets the href attribute on an anchor tag, providing the URI
+   * specified can be loaded according to rules.
+   * @param   element
+   *          The element to set a URI attribute on
+   * @param   attribute
+   *          The attribute of the element to set the URI to, e.g. href or src
+   * @param   uri
+   *          The URI spec to set as the href
+   */
+  _safeSetURIAttribute(element, attribute, uri) {
+    let secman = Cc["@mozilla.org/scriptsecuritymanager;1"].
+                 getService(Ci.nsIScriptSecurityManager);
+    const flags = Ci.nsIScriptSecurityManager.DISALLOW_INHERIT_PRINCIPAL;
+    try {
+      // TODO Is this necessary?
+      secman.checkLoadURIStrWithPrincipal(this._feedPrincipal, uri, flags);
+      // checkLoadURIStrWithPrincipal will throw if the link URI should not be
+      // loaded, either because our feedURI isn't allowed to load it or per
+      // the rules specified in |flags|, so we'll never "linkify" the link...
+    }
+    catch (e) {
+      // Not allowed to load this link because secman.checkLoadURIStr threw
+      return;
+    }
+
+    element.setAttribute(attribute, uri);
+  },
+
+  __bundle: null,
+  get _bundle() {
+    if (!this.__bundle) {
+      this.__bundle = Cc["@mozilla.org/intl/stringbundle;1"].
+                      getService(Ci.nsIStringBundleService).
+                      createBundle(URI_BUNDLE);
+    }
+    return this.__bundle;
+  },
+
+  _getFormattedString(key, params) {
+    return this._bundle.formatStringFromName(key, params, params.length);
+  },
+
+  _getString(key) {
+    return this._bundle.GetStringFromName(key);
+  },
+
+  _setCheckboxCheckedState(aValue) {
+    let checkbox = this._document.getElementById("alwaysUse");
+    if (checkbox) {
+      // see checkbox.xml, xbl bindings are not applied within the sandbox! TODO
+      let change = (aValue != (checkbox.getAttribute("checked") == "true"));
+      if (aValue)
+        checkbox.setAttribute("checked", "true");
+      else
+        checkbox.removeAttribute("checked");
+
+      if (change) {
+        let event = this._document.createEvent("Events");
+        event.initEvent("CheckboxStateChange", true, true);
+        checkbox.dispatchEvent(event);
+      }
+    }
+  },
+
+   /**
+   * Returns a date suitable for displaying in the feed preview.
+   * If the date cannot be parsed, the return value is "false".
+   * @param   dateString
+   *          A date as extracted from a feed entry. (entry.updated)
+   */
+  _parseDate(dateString) {
+    // Convert the date into the user's local time zone
+    let dateObj = new Date(dateString);
+
+    // Make sure the date we're given is valid.
+    if (!dateObj.getTime())
+      return false;
+
+    return this._dateFormatter.format(dateObj);
+  },
+
+  __dateFormatter: null,
+  get _dateFormatter() {
+    if (!this.__dateFormatter) {
+      const locale = Cc["@mozilla.org/chrome/chrome-registry;1"]
+                     .getService(Ci.nsIXULChromeRegistry)
+                     .getSelectedLocale("global", true);
+      const dtOptions = { year: 'numeric', month: 'long', day: 'numeric',
+                          hour: 'numeric', minute: 'numeric' };
+      this.__dateFormatter = new Intl.DateTimeFormat(locale, dtOptions);
+    }
+    return this.__dateFormatter;
+  },
+
+  /**
+   * Returns the feed type.
+   */
+  __feedType: null,
+  _getFeedType() {
+    if (this.__feedType != null)
+      return this.__feedType;
+
+    try {
+      // grab the feed because it's got the feed.type in it.
+      let container = this._getContainer();
+      let feed = container.QueryInterface(Ci.nsIFeed);
+      this.__feedType = feed.type;
+      return feed.type;
+    } catch (ex) { }
+
+    return Ci.nsIFeed.TYPE_FEED;
+  },
+
+  /**
+   * Writes the feed title into the preview document.
+   * @param   container
+   *          The feed container
+   */
+  _setTitleText(container) {
+    if (container.title) {
+      let title = container.title.plainText();
+      this._setContentText(TITLE_ID, container.title);
+      this._document.title = title;
+    }
+
+    let feed = container.QueryInterface(Ci.nsIFeed);
+    if (feed && feed.subtitle)
+      this._setContentText(SUBTITLE_ID, container.subtitle);
+  },
+
+  /**
+   * Writes the title image into the preview document if one is present.
+   * @param   container
+   *          The feed container
+   */
+  _setTitleImage(container) {
+    try {
+      let parts = container.image;
+
+      // Set up the title image (supplied by the feed)
+      let feedTitleImage = this._document.getElementById("feedTitleImage");
+      this._safeSetURIAttribute(feedTitleImage, "src",
+                                parts.getPropertyAsAString("url"));
+
+      // Set up the title image link
+      let feedTitleLink = this._document.getElementById("feedTitleLink");
+
+      let titleText = this._getFormattedString("linkTitleTextFormat",
+                                               [parts.getPropertyAsAString("title")]);
+      let feedTitleText = this._document.getElementById("feedTitleText");
+      let titleImageWidth = parseInt(parts.getPropertyAsAString("width")) + 15;
+
+      // Fix the margin on the main title, so that the image doesn't run over
+      // the underline
+      feedTitleLink.setAttribute('title', titleText);
+      feedTitleText.style.marginRight = titleImageWidth + 'px';
+
+      this._safeSetURIAttribute(feedTitleLink, "href",
+                                parts.getPropertyAsAString("link"));
+    }
+    catch (e) {
+      LOG("Failed to set Title Image (this is benign): " + e);
+    }
+  },
+
+  /**
+   * Writes all entries contained in the feed.
+   * @param   container
+   *          The container of entries in the feed
+   */
+  _writeFeedContent(container) {
+    // Build the actual feed content
+    let feed = container.QueryInterface(Ci.nsIFeed);
+    if (feed.items.length == 0)
+      return;
+
+    let feedContent = this._document.getElementById("feedContent");
+
+    for (let i = 0; i < feed.items.length; ++i) {
+      let entry = feed.items.queryElementAt(i, Ci.nsIFeedEntry);
+      entry.QueryInterface(Ci.nsIFeedContainer);
+
+      let entryContainer = this._document.createElementNS(HTML_NS, "div");
+      entryContainer.className = "entry";
+
+      // If the entry has a title, make it a link
+      if (entry.title) {
+        let a = this._document.createElementNS(HTML_NS, "a");
+        let span = this._document.createElementNS(HTML_NS, "span");
+        a.appendChild(span);
+        if (entry.title.base)
+          span.setAttributeNS(XML_NS, "base", entry.title.base.spec);
+        span.appendChild(entry.title.createDocumentFragment(a));
+
+        // Entries are not required to have links, so entry.link can be null.
+        if (entry.link)
+          this._safeSetURIAttribute(a, "href", entry.link.spec);
+
+        let title = this._document.createElementNS(HTML_NS, "h3");
+        title.appendChild(a);
+
+        let lastUpdated = this._parseDate(entry.updated);
+        if (lastUpdated) {
+          let dateDiv = this._document.createElementNS(HTML_NS, "div");
+          dateDiv.className = "lastUpdated";
+          dateDiv.textContent = lastUpdated;
+          title.appendChild(dateDiv);
+        }
+
+        entryContainer.appendChild(title);
+      }
+
+      let body = this._document.createElementNS(HTML_NS, "div");
+      let summary = entry.summary || entry.content;
+      let docFragment = null;
+      if (summary) {
+        if (summary.base)
+          body.setAttributeNS(XML_NS, "base", summary.base.spec);
+        else
+          LOG("no base?");
+        docFragment = summary.createDocumentFragment(body);
+        if (docFragment)
+          body.appendChild(docFragment);
+
+        // If the entry doesn't have a title, append a # permalink
+        // See http://scripting.com/rss.xml for an example
+        if (!entry.title && entry.link) {
+          let a = this._document.createElementNS(HTML_NS, "a");
+          a.appendChild(this._document.createTextNode("#"));
+          this._safeSetURIAttribute(a, "href", entry.link.spec);
+          body.appendChild(this._document.createTextNode(" "));
+          body.appendChild(a);
+        }
+
+      }
+      body.className = "feedEntryContent";
+      entryContainer.appendChild(body);
+
+      if (entry.enclosures && entry.enclosures.length > 0) {
+        let enclosuresDiv = this._buildEnclosureDiv(entry);
+        entryContainer.appendChild(enclosuresDiv);
+      }
+
+      let clearDiv = this._document.createElementNS(HTML_NS, "div");
+      clearDiv.style.clear = "both";
+
+      feedContent.appendChild(entryContainer);
+      feedContent.appendChild(clearDiv);
+    }
+  },
+
+  /**
+   * Takes a url to a media item and returns the best name it can come up with.
+   * Frequently this is the filename portion (e.g. passing in
+   * http://example.com/foo.mpeg would return "foo.mpeg"), but in more complex
+   * cases, this will return the entire url (e.g. passing in
+   * http://example.com/somedirectory/ would return
+   * http://example.com/somedirectory/).
+   * @param aURL
+   *        The URL string from which to create a display name
+   * @returns a string
+   */
+  _getURLDisplayName(aURL) {
+    let url = makeURI(aURL);
+    url.QueryInterface(Ci.nsIURL);
+    if (url == null || url.fileName.length == 0)
+      return decodeURIComponent(aURL);
+
+    return decodeURIComponent(url.fileName);
+  },
+
+  /**
+   * Takes a FeedEntry with enclosures, generates the HTML code to represent
+   * them, and returns that.
+   * @param   entry
+   *          FeedEntry with enclosures
+   * @returns element
+   */
+  _buildEnclosureDiv(entry) {
+    let enclosuresDiv = this._document.createElementNS(HTML_NS, "div");
+    enclosuresDiv.className = "enclosures";
+
+    enclosuresDiv.appendChild(this._document.createTextNode(this._getString("mediaLabel")));
+
+    for (let i_enc = 0; i_enc < entry.enclosures.length; ++i_enc) {
+      let enc = entry.enclosures.queryElementAt(i_enc, Ci.nsIWritablePropertyBag2);
+
+      if (!(enc.hasKey("url")))
+        continue;
+
+      let enclosureDiv = this._document.createElementNS(HTML_NS, "div");
+      enclosureDiv.setAttribute("class", "enclosure");
+
+      let mozicon = "moz-icon://.txt?size=16";
+      let type_text = null;
+      let size_text = null;
+
+      if (enc.hasKey("type")) {
+        type_text = enc.get("type");
+        if (enc.hasKey("typeDesc"))
+          type_text = enc.get("typeDesc");
+
+        if (type_text && type_text.length > 0)
+          mozicon = "moz-icon://goat?size=16&contentType=" + enc.get("type");
+      }
+
+      if (enc.hasKey("length") && /^[0-9]+$/.test(enc.get("length"))) {
+        let enc_size = convertByteUnits(parseInt(enc.get("length")));
+
+        size_text = this._getFormattedString("enclosureSizeText",
+                                             [enc_size[0],
+                                             this._getString(enc_size[1])]);
+      }
+
+      let iconimg = this._document.createElementNS(HTML_NS, "img");
+      iconimg.setAttribute("src", mozicon);
+      iconimg.setAttribute("class", "type-icon");
+      enclosureDiv.appendChild(iconimg);
+
+      enclosureDiv.appendChild(this._document.createTextNode( " " ));
+
+      let enc_href = this._document.createElementNS(HTML_NS, "a");
+      enc_href.appendChild(this._document.createTextNode(this._getURLDisplayName(enc.get("url"))));
+      this._safeSetURIAttribute(enc_href, "href", enc.get("url"));
+      enclosureDiv.appendChild(enc_href);
+
+      if (type_text && size_text)
+        enclosureDiv.appendChild(this._document.createTextNode( " (" + type_text + ", " + size_text + ")"));
+
+      else if (type_text)
+        enclosureDiv.appendChild(this._document.createTextNode( " (" + type_text + ")"))
+
+      else if (size_text)
+        enclosureDiv.appendChild(this._document.createTextNode( " (" + size_text + ")"))
+
+      enclosuresDiv.appendChild(enclosureDiv);
+    }
+
+    return enclosuresDiv;
+  },
+
+  /**
+   * Gets a valid nsIFeedContainer object from the parsed nsIFeedResult.
+   * Displays error information if there was one.
+   * @returns A valid nsIFeedContainer object containing the contents of
+   *          the feed.
+   */
+  _getContainer() {
+    let feedService =
+        Cc["@mozilla.org/browser/feeds/result-service;1"].
+        getService(Ci.nsIFeedResultService);
+
+    let result;
+    try {
+      result =
+        feedService.getFeedResult(this._getOriginalURI(this._window));
+    }
+    catch (e) {
+      LOG("Subscribe Preview: feed not available?!");
+    }
+
+    if (result.bozo) {
+      LOG("Subscribe Preview: feed result is bozo?!");
+    }
+
+    let container;
+    try {
+      container = result.doc;
+    }
+    catch (e) {
+      LOG("Subscribe Preview: no result.doc? Why didn't the original reload?");
+      return null;
+    }
+    return container;
+  },
+
+  /**
+   * Get moz-icon url for a file
+   * @param   file
+   *          A nsIFile object for which the moz-icon:// is returned
+   * @returns moz-icon url of the given file as a string
+   */
+  _getFileIconURL(file) {
+    let ios = Cc["@mozilla.org/network/io-service;1"].
+              getService(Ci.nsIIOService);
+    let fph = ios.getProtocolHandler("file")
+                 .QueryInterface(Ci.nsIFileProtocolHandler);
+    let urlSpec = fph.getURLSpecFromFile(file);
+    return "moz-icon://" + urlSpec + "?size=16";
+  },
+
+  /**
+   * Displays a prompt from which the user may choose a (client) feed reader.
+   * @param aCallback the callback method, passes in true if a feed reader was
+   *        selected, false otherwise.
+   */
+  _chooseClientApp(aCallback) {
+    this._subscribeCallback = aCallback;
+    this._mm.sendAsyncMessage("FeedWriter:ChooseClientApp",
+                              { title: this._getString("chooseApplicationDialogTitle"),
+                                feedType: this._getFeedType() });
+  },
+
+  _setSubscribeUsingLabel() {
+    let stringLabel = "subscribeFeedUsing";
+    switch (this._getFeedType()) {
+      case Ci.nsIFeed.TYPE_VIDEO:
+        stringLabel = "subscribeVideoPodcastUsing";
+        break;
+
+      case Ci.nsIFeed.TYPE_AUDIO:
+        stringLabel = "subscribeAudioPodcastUsing";
+        break;
+    }
+
+    let subscribeUsing = this._document.getElementById("subscribeUsingDescription");
+    let textNode = this._document.createTextNode(this._getString(stringLabel));
+    subscribeUsing.insertBefore(textNode, subscribeUsing.firstChild);
+  },
+
+  _setAlwaysUseLabel() {
+    let checkbox = this._document.getElementById("alwaysUse");
+    if (checkbox && this._handlersList) {
+      let handlerName = this._handlersList.selectedOptions[0]
+                            .textContent;
+      let stringLabel = "alwaysUseForFeeds";
+      switch (this._getFeedType()) {
+        case Ci.nsIFeed.TYPE_VIDEO:
+          stringLabel = "alwaysUseForVideoPodcasts";
+          break;
+
+        case Ci.nsIFeed.TYPE_AUDIO:
+          stringLabel = "alwaysUseForAudioPodcasts";
+          break;
+      }
+
+      let label = this._getFormattedString(stringLabel, [handlerName]);
+
+      let checkboxText = this._document.getElementById("checkboxText");
+      if (checkboxText.lastChild.nodeType == checkboxText.TEXT_NODE) {
+        checkboxText.lastChild.textContent = label;
+      } else {
+        LOG("FeedWriter._setAlwaysUseLabel: Expected textNode as lastChild of alwaysUse label");
+        let textNode = this._document.createTextNode(label);
+        checkboxText.appendChild(textNode);
+      }
+    }
+  },
+
+  // nsIDomEventListener
+  handleEvent(event) {
+    if (event.target.ownerDocument != this._document) {
+      LOG("FeedWriter.handleEvent: Someone passed the feed writer as a listener to the events of another document!");
+      return;
+    }
+
+    switch (event.type) {
+      case "click":
+        if (event.target.id == "subscribeButton") {
+          this.subscribe();
+        }
+      break;
+      case "change":
+        LOG("Change fired");
+        if (event.target.selectedOptions[0].id == "chooseApplicationMenuItem") {
+          this._chooseClientApp(() => {
+            // Select the (per-prefs) selected handler if no application
+            // was selected
+            LOG("Selected handler after callback");
+            this._setAlwaysUseLabel();
+          });
+        } else {
+          this._setAlwaysUseLabel();
+        }
+        break;
+    }
+  },
+
+  _getWebHandlerElementsForURL(aURL) {
+    return this._handlersList.querySelectorAll('[webhandlerurl="' + aURL + '"]');
+  },
+
+  _setSelectedHandlerResponse(handler, url) {
+    LOG(`Selecting handler response ${handler} ${url}`);
+    switch (handler) {
+      case "web": {
+        if (this._handlersList) {
+          let handlers =
+            this._getWebHandlerElementsForURL(url);
+          if (handlers.length == 0) {
+            LOG(`Selected web handler isn't in the menulist ${url}`);
+            return;
+          }
+
+          handlers[0].selected = true;
+        }
+        break;
+      }
+      case "client":
+      case "default":
+        // do nothing, these are handled by the onchange event
+        break;
+      case "bookmarks":
+      default: {
+        let liveBookmarksMenuItem = this._document.getElementById("liveBookmarksMenuItem");
+        if (liveBookmarksMenuItem)
+          liveBookmarksMenuItem.selected = true;
+      }
+    }
+  },
+
+  _initSubscriptionUI(setupMessage) {
+    if (!this._handlersList)
+      return;
+    LOG("UI init");
+
+    let feedType = this._getFeedType();
+
+    // change the background
+    let header = this._document.getElementById("feedHeader");
+    switch (feedType) {
+      case Ci.nsIFeed.TYPE_VIDEO:
+        header.className = 'videoPodcastBackground';
+        break;
+
+      case Ci.nsIFeed.TYPE_AUDIO:
+        header.className = 'audioPodcastBackground';
+        break;
+
+      default:
+        header.className = 'feedBackground';
+    }
+
+    let liveBookmarksMenuItem = this._document.getElementById("liveBookmarksMenuItem");
+
+    // Last-selected application
+    let menuItem = liveBookmarksMenuItem.cloneNode(false);
+    menuItem.removeAttribute("selected");
+    menuItem.setAttribute("id", "selectedAppMenuItem");
+    menuItem.setAttribute("handlerType", "client");
+
+    // Hide the menuitem until we select an app
+    menuItem.style.display = "none";
+    this._selectedAppMenuItem = menuItem;
+
+    this._handlersList.appendChild(this._selectedAppMenuItem);
+
+    // Create the menuitem for the default reader, but don't show/populate it until
+    // we get confirmation of what it is from the parent
+    menuItem = liveBookmarksMenuItem.cloneNode(false);
+    menuItem.removeAttribute("selected");
+    menuItem.setAttribute("id", "defaultHandlerMenuItem");
+    menuItem.setAttribute("handlerType", "client");
+    menuItem.style.display = "none";
+
+    this._defaultHandlerMenuItem = menuItem;
+    this._handlersList.appendChild(this._defaultHandlerMenuItem);
+
+    // "Choose Application..." menuitem
+    menuItem = liveBookmarksMenuItem.cloneNode(false);
+    menuItem.removeAttribute("selected");
+    menuItem.setAttribute("id", "chooseApplicationMenuItem");
+    menuItem.textContent = this._getString("chooseApplicationMenuItem");
+
+    this._handlersList.appendChild(menuItem);
+
+    // separator
+    let chooseAppSep = liveBookmarksMenuItem.nextElementSibling.cloneNode(false);
+    chooseAppSep.textContent = liveBookmarksMenuItem.nextElementSibling.textContent;
+    this._handlersList.appendChild(chooseAppSep);
+
+    for (let handler of setupMessage.handlers) {
+      if (!handler.uri) {
+        LOG("Handler with name " + handler.name + " has no URI!? Skipping...");
+        continue;
+      }
+      menuItem = liveBookmarksMenuItem.cloneNode(false);
+      menuItem.removeAttribute("selected");
+      menuItem.className = "menuitem-iconic";
+      menuItem.textContent = handler.name;
+      menuItem.setAttribute("handlerType", "web");
+      menuItem.setAttribute("webhandlerurl", handler.uri);
+      this._handlersList.appendChild(menuItem);
+    }
+
+    this._setSelectedHandlerResponse(setupMessage.reader.handler, setupMessage.reader.url);
+
+    if (setupMessage.defaultMenuItem) {
+      LOG(`Setting default menu item ${setupMessage.defaultMenuItem}`);
+      this._setApplicationLauncherMenuItem(this._defaultHandlerMenuItem, setupMessage.defaultMenuItem);
+    }
+    if (setupMessage.selectedMenuItem) {
+      LOG(`Setting selected menu item ${setupMessage.selectedMenuItem}`);
+      this._setApplicationLauncherMenuItem(this._selectedAppMenuItem, setupMessage.selectedMenuItem);
+    }
+
+    // "Subscribe using..."
+    this._setSubscribeUsingLabel();
+
+    // "Always use..." checkbox initial state
+    this._setCheckboxCheckedState(setupMessage.reader.alwaysUse);
+    this._setAlwaysUseLabel();
+
+    // We update the "Always use.." checkbox label whenever the selected item
+    // in the list is changed
+    this._handlersList.addEventListener("change", this);
+
+    // Set up the "Subscribe Now" button
+    this._document.getElementById("subscribeButton")
+        .addEventListener("click", this);
+
+    // first-run ui
+    if (setupMessage.showFirstRunUI) {
+      let textfeedinfo1, textfeedinfo2;
+      switch (feedType) {
+        case Ci.nsIFeed.TYPE_VIDEO:
+          textfeedinfo1 = "feedSubscriptionVideoPodcast1";
+          textfeedinfo2 = "feedSubscriptionVideoPodcast2";
+          break;
+        case Ci.nsIFeed.TYPE_AUDIO:
+          textfeedinfo1 = "feedSubscriptionAudioPodcast1";
+          textfeedinfo2 = "feedSubscriptionAudioPodcast2";
+          break;
+        default:
+          textfeedinfo1 = "feedSubscriptionFeed1";
+          textfeedinfo2 = "feedSubscriptionFeed2";
+      }
+
+      let feedinfo1 = this._document.getElementById("feedSubscriptionInfo1");
+      let feedinfo1Str = this._getString(textfeedinfo1);
+      let feedinfo2 = this._document.getElementById("feedSubscriptionInfo2");
+      let feedinfo2Str = this._getString(textfeedinfo2);
+
+      feedinfo1.textContent = feedinfo1Str;
+      feedinfo2.textContent = feedinfo2Str;
+
+      header.setAttribute('firstrun', 'true');
+
+      this._mm.sendAsyncMessage("FeedWriter:ShownFirstRun");
+    }
+  },
+
+  /**
+   * Returns the original URI object of the feed and ensures that this
+   * component is only ever invoked from the preview document.
+   * @param aWindow
+   *        The window of the document invoking the BrowserFeedWriter
+   */
+  _getOriginalURI(aWindow) {
+    let docShell = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                          .getInterface(Ci.nsIWebNavigation)
+                          .QueryInterface(Ci.nsIDocShell);
+    let chan = docShell.currentDocumentChannel;
+
+    // We probably need to call InheritFromDocShellToDoc for this, but right now
+    // we can't call it from JS.
+    let attrs = docShell.getOriginAttributes();
+    let ssm = Services.scriptSecurityManager;
+    let nullPrincipal = ssm.createNullPrincipal(attrs);
+
+    // this channel is not going to be openend, use a nullPrincipal
+    // and the most restrctive securityFlag.
+    let resolvedURI = NetUtil.newChannel({
+      uri: "about:feeds",
+      loadingPrincipal: nullPrincipal,
+      securityFlags: Ci.nsILoadInfo.SEC_REQUIRE_SAME_ORIGIN_DATA_IS_BLOCKED,
+      contentPolicyType: Ci.nsIContentPolicy.TYPE_OTHER
+    }).URI;
+
+    if (resolvedURI.equals(chan.URI))
+      return chan.originalURI;
+
+    return null;
+  },
+
+  _window: null,
+  _document: null,
+  _feedURI: null,
+  _feedPrincipal: null,
+  _handlersList: null,
+
+  // BrowserFeedWriter WebIDL methods
+  init(aWindow) {
+    let window = aWindow;
+    this._feedURI = this._getOriginalURI(window);
+    if (!this._feedURI)
+      return;
+
+    this._window = window;
+    this._document = window.document;
+    this._handlersList = this._document.getElementById("handlersMenuList");
+
+    let secman = Cc["@mozilla.org/scriptsecuritymanager;1"].
+                 getService(Ci.nsIScriptSecurityManager);
+    this._feedPrincipal = secman.createCodebasePrincipal(this._feedURI, {});
+
+    LOG("Subscribe Preview: feed uri = " + this._window.location.href);
+
+
+    this._mm.addMessageListener("FeedWriter:PreferenceUpdated", this);
+    this._mm.addMessageListener("FeedWriter:SetApplicationLauncherMenuItem", this);
+    this._mm.addMessageListener("FeedWriter:GetSubscriptionUIResponse", this);
+    this._mm.addMessageListener("FeedWriter:SetFeedPrefsAndSubscribeResponse", this);
+
+    const feedType = this._getFeedType();
+    this._mm.sendAsyncMessage("FeedWriter:GetSubscriptionUI",
+                              { feedType });
+  },
+
+  receiveMessage(msg) {
+    if (!this._window) {
+      // this._window is null unless this.init was called with a trusted
+      // window object.
+      return;
+    }
+    LOG(`received message from parent ${msg.name}`);
+    switch (msg.name) {
+      case "FeedWriter:PreferenceUpdated":
+        // This is called when browser-feeds.js spots a pref change
+        // This will happen when
+        // - about:preferences#applications changes
+        // - another feed reader page changes the preference
+        // - when this page itself changes the select and there isn't a redirect
+        //   bookmarks and launching an external app means the page stays open after subscribe
+        const feedType = this._getFeedType();
+        LOG(`Got prefChange! ${JSON.stringify(msg.data)} current type: ${feedType}`);
+        let feedTypePref = msg.data.default;
+        if (feedType in msg.data) {
+          feedTypePref = msg.data[feedType];
+        }
+        LOG(`Got pref ${JSON.stringify(feedTypePref)}`);
+        this._setCheckboxCheckedState(feedTypePref.alwaysUse);
+        this._setSelectedHandlerResponse(feedTypePref.handler, feedTypePref.url);
+        this._setAlwaysUseLabel();
+        break;
+      case "FeedWriter:SetFeedPrefsAndSubscribeResponse":
+        LOG(`FeedWriter:SetFeedPrefsAndSubscribeResponse - Redirecting ${msg.data.redirect}`);
+        this._window.location.href = msg.data.redirect;
+        break;
+      case "FeedWriter:GetSubscriptionUIResponse":
+        // Set up the subscription UI
+        this._initSubscriptionUI(msg.data);
+        break;
+      case "FeedWriter:SetApplicationLauncherMenuItem":
+        LOG(`FeedWriter:SetApplicationLauncherMenuItem - picked ${msg.data.name}`);
+        this._setApplicationLauncherMenuItem(this._selectedAppMenuItem, msg.data.name);
+        // Potentially a bit racy, but I don't think we can get into a state where this callback is set and
+        // we're not coming back from ChooseClientApp in browser-feeds.js
+        if (this._subscribeCallback) {
+          this._subscribeCallback();
+          this._subscribeCallback = null;
+        }
+        break;
+    }
+  },
+
+  _setApplicationLauncherMenuItem(menuItem, aName) {
+    /* unselect all handlers */
+    [...this._handlersList.children].forEach((option) => {
+      option.removeAttribute("selected");
+    });
+    menuItem.textContent = aName;
+    menuItem.style.display = "";
+    menuItem.selected = true;
+  },
+
+  writeContent() {
+    if (!this._window)
+      return;
+
+    try {
+      // Set up the feed content
+      let container = this._getContainer();
+      if (!container)
+        return;
+
+      this._setTitleText(container);
+      this._setTitleImage(container);
+      this._writeFeedContent(container);
+    }
+    finally {
+      this._removeFeedFromCache();
+    }
+  },
+
+  close() {
+    this._document.getElementById("subscribeButton")
+        .removeEventListener("click", this, false);
+    this._handlersList
+        .removeEventListener("change", this, false);
+    this._document = null;
+    this._window = null;
+    this._handlersList = null;
+
+    this._removeFeedFromCache();
+    this.__bundle = null;
+    this._feedURI = null;
+
+    this._selectedApp = undefined;
+    this._selectedAppMenuItem = null;
+    this._defaultHandlerMenuItem = null;
+  },
+
+  _removeFeedFromCache() {
+    if (this._feedURI) {
+      let feedService = Cc["@mozilla.org/browser/feeds/result-service;1"].
+                        getService(Ci.nsIFeedResultService);
+      feedService.removeFeedResult(this._feedURI);
+      this._feedURI = null;
+    }
+  },
+
+  subscribe() {
+    let feedType = this._getFeedType();
+
+    // Subscribe to the feed using the selected handler and save prefs
+    let defaultHandler = "reader";
+    let useAsDefault = this._document.getElementById("alwaysUse").getAttribute("checked");
+
+    let selectedItem = this._handlersList.selectedOptions[0];
+    let subscribeCallback = () => {
+      let feedReader = null;
+      let settings = {
+        feedType,
+        useAsDefault,
+        // Pull the title and subtitle out of the document
+        feedTitle: this._document.getElementById(TITLE_ID).textContent,
+        feedSubtitle: this._document.getElementById(SUBTITLE_ID).textContent,
+        feedLocation: this._window.location.href
+      };
+      if (selectedItem.hasAttribute("webhandlerurl")) {
+        feedReader = "web";
+        settings.uri = selectedItem.getAttribute("webhandlerurl");
+      } else {
+        switch (selectedItem.id) {
+          case "selectedAppMenuItem":
+            feedReader = "client";
+            break;
+          case "defaultHandlerMenuItem":
+            feedReader = "default";
+            break;
+          case "liveBookmarksMenuItem":
+            defaultHandler = "bookmarks";
+            feedReader = "bookmarks";
+            break;
+        }
+      }
+      settings.reader = feedReader;
+
+      // If "Always use..." is checked, we should set PREF_*SELECTED_ACTION
+      // to either "reader" (If a web reader or if an application is selected),
+      // or to "bookmarks" (if the live bookmarks option is selected).
+      // Otherwise, we should set it to "ask"
+      if (!useAsDefault) {
+        defaultHandler = "ask";
+      }
+      settings.action = defaultHandler;
+      LOG(`FeedWriter:SetFeedPrefsAndSubscribe - ${JSON.stringify(settings)}`);
+      this._mm.sendAsyncMessage("FeedWriter:SetFeedPrefsAndSubscribe",
+                                settings);
+    }
+
+    // Show the file picker before subscribing if the
+    // choose application menuitem was chosen using the keyboard
+    if (selectedItem.id == "chooseApplicationMenuItem") {
+      this._chooseClientApp(function(aResult) {
+        if (aResult) {
+          selectedItem =
+            this._handlersList.selectedOptions[0];
+          subscribeCallback();
+        }
+      }.bind(this));
+    } else {
+      subscribeCallback();
+    }
+  },
+
+  get _mm() {
+    let mm = this._window.QueryInterface(Ci.nsIInterfaceRequestor).
+                          getInterface(Ci.nsIDocShell).
+                          QueryInterface(Ci.nsIInterfaceRequestor).
+                          getInterface(Ci.nsIContentFrameMessageManager);
+    delete this._mm;
+    return this._mm = mm;
+  },
+
+  classID: FEEDWRITER_CID,
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDOMEventListener, Ci.nsIObserver,
+                                         Ci.nsINavHistoryObserver,
+                                         Ci.nsIDOMGlobalPropertyInitializer])
+};
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([FeedWriter]);
diff --git a/browser/components/feeds/WebContentConverter.js b/browser/components/feeds/WebContentConverter.js
new file mode 100644
index 000000000..2cb5cd145
--- /dev/null
+++ b/browser/components/feeds/WebContentConverter.js
@@ -0,0 +1,1071 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* 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/. */
+
+Components.utils.import("resource://gre/modules/Services.jsm");
+Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
+Components.utils.import("resource://gre/modules/PrivateBrowsingUtils.jsm");
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+
+function LOG(str) {
+  dump("*** " + str + "\n");
+}
+
+const WCCR_CONTRACTID = "@mozilla.org/embeddor.implemented/web-content-handler-registrar;1";
+const WCCR_CLASSID = Components.ID("{792a7e82-06a0-437c-af63-b2d12e808acc}");
+
+const WCC_CLASSID = Components.ID("{db7ebf28-cc40-415f-8a51-1b111851df1e}");
+const WCC_CLASSNAME = "Web Service Handler";
+
+const TYPE_MAYBE_FEED = "application/vnd.mozilla.maybe.feed";
+const TYPE_ANY = "*/*";
+
+const PREF_CONTENTHANDLERS_AUTO = "browser.contentHandlers.auto.";
+const PREF_CONTENTHANDLERS_BRANCH = "browser.contentHandlers.types.";
+const PREF_SELECTED_WEB = "browser.feeds.handlers.webservice";
+const PREF_SELECTED_ACTION = "browser.feeds.handler";
+const PREF_SELECTED_READER = "browser.feeds.handler.default";
+const PREF_HANDLER_EXTERNAL_PREFIX = "network.protocol-handler.external";
+const PREF_ALLOW_DIFFERENT_HOST = "gecko.handlerService.allowRegisterFromDifferentHost";
+
+const STRING_BUNDLE_URI = "chrome://browser/locale/feeds/subscribe.properties";
+
+const NS_ERROR_MODULE_DOM = 2152923136;
+const NS_ERROR_DOM_SYNTAX_ERR = NS_ERROR_MODULE_DOM + 12;
+
+function WebContentConverter() {
+}
+WebContentConverter.prototype = {
+  convert() { },
+  asyncConvertData() { },
+  onDataAvailable() { },
+  onStopRequest() { },
+
+  onStartRequest(request, context) {
+    let wccr =
+        Cc[WCCR_CONTRACTID].
+        getService(Ci.nsIWebContentConverterService);
+    wccr.loadPreferredHandler(request);
+  },
+
+  QueryInterface(iid) {
+    if (iid.equals(Ci.nsIStreamConverter) ||
+        iid.equals(Ci.nsIStreamListener) ||
+        iid.equals(Ci.nsISupports))
+      return this;
+    throw Cr.NS_ERROR_NO_INTERFACE;
+  }
+};
+
+let WebContentConverterFactory = {
+  createInstance(outer, iid) {
+    if (outer != null)
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    return new WebContentConverter().QueryInterface(iid);
+  },
+
+  QueryInterface(iid) {
+    if (iid.equals(Ci.nsIFactory) ||
+        iid.equals(Ci.nsISupports))
+      return this;
+    throw Cr.NS_ERROR_NO_INTERFACE;
+  }
+};
+
+function ServiceInfo(contentType, uri, name) {
+  this._contentType = contentType;
+  this._uri = uri;
+  this._name = name;
+}
+ServiceInfo.prototype = {
+  /**
+   * See nsIHandlerApp
+   */
+  get name() {
+    return this._name;
+  },
+
+  /**
+   * See nsIHandlerApp
+   */
+  equals(aHandlerApp) {
+    if (!aHandlerApp)
+      throw Cr.NS_ERROR_NULL_POINTER;
+
+    if (aHandlerApp instanceof Ci.nsIWebContentHandlerInfo &&
+        aHandlerApp.contentType == this.contentType &&
+        aHandlerApp.uri == this.uri)
+      return true;
+
+    return false;
+  },
+
+  /**
+   * See nsIWebContentHandlerInfo
+   */
+  get contentType() {
+    return this._contentType;
+  },
+
+  /**
+   * See nsIWebContentHandlerInfo
+   */
+  get uri() {
+    return this._uri;
+  },
+
+  /**
+   * See nsIWebContentHandlerInfo
+   */
+  getHandlerURI(uri) {
+    return this._uri.replace(/%s/gi, encodeURIComponent(uri));
+  },
+
+  QueryInterface(iid) {
+    if (iid.equals(Ci.nsIWebContentHandlerInfo) ||
+        iid.equals(Ci.nsISupports))
+      return this;
+    throw Cr.NS_ERROR_NO_INTERFACE;
+  }
+};
+
+const Utils = {
+  makeURI(aURL, aOriginCharset, aBaseURI) {
+    return Services.io.newURI(aURL, aOriginCharset, aBaseURI);
+  },
+
+  checkAndGetURI(aURIString, aContentWindow) {
+    let uri;
+    try {
+      let baseURI = aContentWindow.document.baseURIObject;
+      uri = this.makeURI(aURIString, null, baseURI);
+    } catch (ex) {
+      throw NS_ERROR_DOM_SYNTAX_ERR;
+    }
+
+    // For security reasons we reject non-http(s) urls (see bug 354316),
+    // we may need to revise this once we support more content types
+    if (uri.scheme != "http" && uri.scheme != "https") {
+      throw this.getSecurityError(
+        "Permission denied to add " + uri.spec + " as a content or protocol handler",
+        aContentWindow);
+    }
+
+    // We also reject handlers registered from a different host (see bug 402287)
+    // The pref allows us to test the feature
+    let pb = Services.prefs;
+    if (!pb.getBoolPref(PREF_ALLOW_DIFFERENT_HOST) &&
+        (!["http:", "https:"].includes(aContentWindow.location.protocol) ||
+         aContentWindow.location.hostname != uri.host)) {
+      throw this.getSecurityError(
+        "Permission denied to add " + uri.spec + " as a content or protocol handler",
+        aContentWindow);
+    }
+
+    // If the uri doesn't contain '%s', it won't be a good handler
+    if (uri.spec.indexOf("%s") < 0)
+      throw NS_ERROR_DOM_SYNTAX_ERR;
+
+    return uri;
+  },
+
+  // NB: Throws if aProtocol is not allowed.
+  checkProtocolHandlerAllowed(aProtocol, aURIString, aWindowOrNull) {
+    // First, check to make sure this isn't already handled internally (we don't
+    // want to let them take over, say "chrome").
+    let handler = Services.io.getProtocolHandler(aProtocol);
+    if (!(handler instanceof Ci.nsIExternalProtocolHandler)) {
+      // This is handled internally, so we don't want them to register
+      throw this.getSecurityError(
+        `Permission denied to add ${aURIString} as a protocol handler`,
+        aWindowOrNull);
+    }
+
+    // check if it is in the black list
+    let pb = Services.prefs;
+    let allowed;
+    try {
+      allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "." + aProtocol);
+    }
+    catch (e) {
+      allowed = pb.getBoolPref(PREF_HANDLER_EXTERNAL_PREFIX + "-default");
+    }
+    if (!allowed) {
+      throw this.getSecurityError(
+        `Not allowed to register a protocol handler for ${aProtocol}`,
+        aWindowOrNull);
+    }
+  },
+
+  // Return a SecurityError exception from the given Window if one is given.  If
+  // none is given, just return the given error string, for lack of anything
+  // better.
+  getSecurityError(errorString, aWindowOrNull) {
+    if (!aWindowOrNull) {
+      return errorString;
+    }
+
+    return new aWindowOrNull.DOMException(errorString, "SecurityError");
+  },
+
+  /**
+   * Mappings from known feed types to our internal content type.
+   */
+  _mappings: {
+    "application/rss+xml": TYPE_MAYBE_FEED,
+    "application/atom+xml": TYPE_MAYBE_FEED,
+  },
+
+  resolveContentType(aContentType) {
+    if (aContentType in this._mappings)
+      return this._mappings[aContentType];
+    return aContentType;
+  }
+};
+
+function WebContentConverterRegistrar() {
+  this._contentTypes = {};
+  this._autoHandleContentTypes = {};
+}
+
+WebContentConverterRegistrar.prototype = {
+  get stringBundle() {
+    let sb = Services.strings.createBundle(STRING_BUNDLE_URI);
+    delete WebContentConverterRegistrar.prototype.stringBundle;
+    return WebContentConverterRegistrar.prototype.stringBundle = sb;
+  },
+
+  _getFormattedString(key, params) {
+    return this.stringBundle.formatStringFromName(key, params, params.length);
+  },
+
+  _getString(key) {
+    return this.stringBundle.GetStringFromName(key);
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  getAutoHandler(contentType) {
+    contentType = Utils.resolveContentType(contentType);
+    if (contentType in this._autoHandleContentTypes)
+      return this._autoHandleContentTypes[contentType];
+    return null;
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  setAutoHandler(contentType, handler) {
+    if (handler && !this._typeIsRegistered(contentType, handler.uri))
+      throw Cr.NS_ERROR_NOT_AVAILABLE;
+
+    contentType = Utils.resolveContentType(contentType);
+    this._setAutoHandler(contentType, handler);
+
+    let ps = Services.prefs;
+    let autoBranch = ps.getBranch(PREF_CONTENTHANDLERS_AUTO);
+    if (handler)
+      autoBranch.setCharPref(contentType, handler.uri);
+    else if (autoBranch.prefHasUserValue(contentType))
+      autoBranch.clearUserPref(contentType);
+
+    ps.savePrefFile(null);
+  },
+
+  /**
+   * Update the internal data structure (not persistent)
+   */
+  _setAutoHandler(contentType, handler) {
+    if (handler)
+      this._autoHandleContentTypes[contentType] = handler;
+    else if (contentType in this._autoHandleContentTypes)
+      delete this._autoHandleContentTypes[contentType];
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  getWebContentHandlerByURI(contentType, uri) {
+    return this.getContentHandlers(contentType)
+               .find(e => e.uri == uri) || null;
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  loadPreferredHandler(request) {
+    let channel = request.QueryInterface(Ci.nsIChannel);
+    let contentType = Utils.resolveContentType(channel.contentType);
+    let handler = this.getAutoHandler(contentType);
+    if (handler) {
+      request.cancel(Cr.NS_ERROR_FAILURE);
+
+      let webNavigation =
+          channel.notificationCallbacks.getInterface(Ci.nsIWebNavigation);
+      webNavigation.loadURI(handler.getHandlerURI(channel.URI.spec),
+                            Ci.nsIWebNavigation.LOAD_FLAGS_NONE,
+                            null, null, null);
+    }
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  removeProtocolHandler(aProtocol, aURITemplate) {
+    let eps = Cc["@mozilla.org/uriloader/external-protocol-service;1"].
+              getService(Ci.nsIExternalProtocolService);
+    let handlerInfo = eps.getProtocolHandlerInfo(aProtocol);
+    let handlers =  handlerInfo.possibleApplicationHandlers;
+    for (let i = 0; i < handlers.length; i++) {
+      try { // We only want to test web handlers
+        let handler = handlers.queryElementAt(i, Ci.nsIWebHandlerApp);
+        if (handler.uriTemplate == aURITemplate) {
+          handlers.removeElementAt(i);
+          let hs = Cc["@mozilla.org/uriloader/handler-service;1"].
+                   getService(Ci.nsIHandlerService);
+          hs.store(handlerInfo);
+          return;
+        }
+      } catch (e) { /* it wasn't a web handler */ }
+    }
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  removeContentHandler(contentType, uri) {
+    function notURI(serviceInfo) {
+      return serviceInfo.uri != uri;
+    }
+
+    if (contentType in this._contentTypes) {
+      this._contentTypes[contentType] =
+        this._contentTypes[contentType].filter(notURI);
+    }
+  },
+
+  /**
+   * These are types for which there is a separate content converter aside
+   * from our built in generic one. We should not automatically register
+   * a factory for creating a converter for these types.
+   */
+  _blockedTypes: {
+    "application/vnd.mozilla.maybe.feed": true,
+  },
+
+  /**
+   * Determines if a web handler is already registered.
+   *
+   * @param aProtocol
+   *        The scheme of the web handler we are checking for.
+   * @param aURITemplate
+   *        The URI template that the handler uses to handle the protocol.
+   * @return true if it is already registered, false otherwise.
+   */
+  _protocolHandlerRegistered(aProtocol, aURITemplate) {
+    let eps = Cc["@mozilla.org/uriloader/external-protocol-service;1"].
+              getService(Ci.nsIExternalProtocolService);
+    let handlerInfo = eps.getProtocolHandlerInfo(aProtocol);
+    let handlers =  handlerInfo.possibleApplicationHandlers;
+    for (let i = 0; i < handlers.length; i++) {
+      try { // We only want to test web handlers
+        let handler = handlers.queryElementAt(i, Ci.nsIWebHandlerApp);
+        if (handler.uriTemplate == aURITemplate)
+          return true;
+      } catch (e) { /* it wasn't a web handler */ }
+    }
+    return false;
+  },
+
+  /**
+   * See nsIWebContentHandlerRegistrar
+   */
+  registerProtocolHandler(aProtocol, aURIString, aTitle, aBrowserOrWindow) {
+    LOG("registerProtocolHandler(" + aProtocol + "," + aURIString + "," + aTitle + ")");
+    let haveWindow = (aBrowserOrWindow instanceof Ci.nsIDOMWindow);
+    let uri;
+    if (haveWindow) {
+      uri = Utils.checkAndGetURI(aURIString, aBrowserOrWindow);
+    } else {
+      // aURIString must not be a relative URI.
+      uri = Utils.makeURI(aURIString, null);
+    }
+
+    // If the protocol handler is already registered, just return early.
+    if (this._protocolHandlerRegistered(aProtocol, uri.spec)) {
+      return;
+    }
+
+    let browser;
+    if (haveWindow) {
+      let browserWindow =
+        this._getBrowserWindowForContentWindow(aBrowserOrWindow);
+      browser = this._getBrowserForContentWindow(browserWindow,
+                                                 aBrowserOrWindow);
+    } else {
+      browser = aBrowserOrWindow;
+    }
+    if (PrivateBrowsingUtils.isBrowserPrivate(browser)) {
+      // Inside the private browsing mode, we don't want to alert the user to save
+      // a protocol handler.  We log it to the error console so that web developers
+      // would have some way to tell what's going wrong.
+      Services.console.
+      logStringMessage("Web page denied access to register a protocol handler inside private browsing mode");
+      return;
+    }
+
+    Utils.checkProtocolHandlerAllowed(aProtocol, aURIString,
+                                      haveWindow ? aBrowserOrWindow : null);
+
+    // Now Ask the user and provide the proper callback
+    let message = this._getFormattedString("addProtocolHandler",
+                                           [aTitle, uri.host, aProtocol]);
+
+    let notificationIcon = uri.prePath + "/favicon.ico";
+    let notificationValue = "Protocol Registration: " + aProtocol;
+    let addButton = {
+      label: this._getString("addProtocolHandlerAddButton"),
+      accessKey: this._getString("addProtocolHandlerAddButtonAccesskey"),
+      protocolInfo: { protocol: aProtocol, uri: uri.spec, name: aTitle },
+
+      callback(aNotification, aButtonInfo) {
+          let protocol = aButtonInfo.protocolInfo.protocol;
+          let uri      = aButtonInfo.protocolInfo.uri;
+          let name     = aButtonInfo.protocolInfo.name;
+
+          let handler = Cc["@mozilla.org/uriloader/web-handler-app;1"].
+                        createInstance(Ci.nsIWebHandlerApp);
+          handler.name = name;
+          handler.uriTemplate = uri;
+
+          let eps = Cc["@mozilla.org/uriloader/external-protocol-service;1"].
+                    getService(Ci.nsIExternalProtocolService);
+          let handlerInfo = eps.getProtocolHandlerInfo(protocol);
+          handlerInfo.possibleApplicationHandlers.appendElement(handler, false);
+
+          // Since the user has agreed to add a new handler, chances are good
+          // that the next time they see a handler of this type, they're going
+          // to want to use it.  Reset the handlerInfo to ask before the next
+          // use.
+          handlerInfo.alwaysAskBeforeHandling = true;
+
+          let hs = Cc["@mozilla.org/uriloader/handler-service;1"].
+                   getService(Ci.nsIHandlerService);
+          hs.store(handlerInfo);
+        }
+    };
+    let notificationBox = browser.getTabBrowser().getNotificationBox(browser);
+    notificationBox.appendNotification(message,
+                                       notificationValue,
+                                       notificationIcon,
+                                       notificationBox.PRIORITY_INFO_LOW,
+                                       [addButton]);
+  },
+
+  /**
+   * See nsIWebContentHandlerRegistrar
+   * If a DOM window is provided, then the request came from content, so we
+   * prompt the user to confirm the registration.
+   */
+  registerContentHandler(aContentType, aURIString, aTitle, aWindowOrBrowser) {
+    LOG("registerContentHandler(" + aContentType + "," + aURIString + "," + aTitle + ")");
+
+    // Make sure to do our URL checks up front, before our content type check,
+    // just like the WebContentConverterRegistrarContent does.
+    let haveWindow = aWindowOrBrowser &&
+                     (aWindowOrBrowser instanceof Ci.nsIDOMWindow);
+    let uri;
+    if (haveWindow) {
+      uri = Utils.checkAndGetURI(aURIString, aWindowOrBrowser);
+    } else if (aWindowOrBrowser) {
+      // uri was vetted in the content process.
+      uri = Utils.makeURI(aURIString, null);
+    }
+
+    // We only support feed types at present.
+    let contentType = Utils.resolveContentType(aContentType);
+    // XXX We should be throwing a Utils.getSecurityError() here in at least
+    // some cases.  See bug 1266492.
+    if (contentType != TYPE_MAYBE_FEED) {
+      return;
+    }
+
+    if (aWindowOrBrowser) {
+      let notificationBox;
+      if (haveWindow) {
+        let browserWindow = this._getBrowserWindowForContentWindow(aWindowOrBrowser);
+        let browserElement = this._getBrowserForContentWindow(browserWindow, aWindowOrBrowser);
+        notificationBox = browserElement.getTabBrowser().getNotificationBox(browserElement);
+      } else {
+        notificationBox = aWindowOrBrowser.getTabBrowser()
+                                          .getNotificationBox(aWindowOrBrowser);
+      }
+
+      this._appendFeedReaderNotification(uri, aTitle, notificationBox);
+    }
+    else {
+      this._registerContentHandler(contentType, aURIString, aTitle);
+    }
+  },
+
+  /**
+   * Returns the browser chrome window in which the content window is in
+   */
+  _getBrowserWindowForContentWindow(aContentWindow) {
+    return aContentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIWebNavigation)
+                         .QueryInterface(Ci.nsIDocShellTreeItem)
+                         .rootTreeItem
+                         .QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIDOMWindow)
+                         .wrappedJSObject;
+  },
+
+  /**
+   * Returns the <xul:browser> element associated with the given content
+   * window.
+   *
+   * @param aBrowserWindow
+   *        The browser window in which the content window is in.
+   * @param aContentWindow
+   *        The content window. It's possible to pass a child content window
+   *        (i.e. the content window of a frame/iframe).
+   */
+  _getBrowserForContentWindow(aBrowserWindow, aContentWindow) {
+    // This depends on pseudo APIs of browser.js and tabbrowser.xml
+    aContentWindow = aContentWindow.top;
+    return aBrowserWindow.gBrowser.browsers.find((browser) =>
+      browser.contentWindow == aContentWindow);
+  },
+
+  /**
+   * Appends a notifcation for the given feed reader details.
+   *
+   * The notification could be either a pseudo-dialog which lets
+   * the user to add the feed reader:
+   * [ [icon] Add %feed-reader-name% (%feed-reader-host%) as a Feed Reader?  (Add) [x] ]
+   *
+   * or a simple message for the case where the feed reader is already registered:
+   * [ [icon] %feed-reader-name% is already registered as a Feed Reader             [x] ]
+   *
+   * A new notification isn't appended if the given notificationbox has a
+   * notification for the same feed reader.
+   *
+   * @param aURI
+   *        The url of the feed reader as a nsIURI object
+   * @param aName
+   *        The feed reader name as it was passed to registerContentHandler
+   * @param aNotificationBox
+   *        The notification box to which a notification might be appended
+   * @return true if a notification has been appended, false otherwise.
+   */
+  _appendFeedReaderNotification(aURI, aName, aNotificationBox) {
+    let uriSpec = aURI.spec;
+    let notificationValue = "feed reader notification: " + uriSpec;
+    let notificationIcon = aURI.prePath + "/favicon.ico";
+
+    // Don't append a new notification if the notificationbox
+    // has a notification for the given feed reader already
+    if (aNotificationBox.getNotificationWithValue(notificationValue))
+      return false;
+
+    let buttons;
+    let message;
+    if (this.getWebContentHandlerByURI(TYPE_MAYBE_FEED, uriSpec))
+      message = this._getFormattedString("handlerRegistered", [aName]);
+    else {
+      message = this._getFormattedString("addHandler", [aName, aURI.host]);
+      let self = this;
+      let addButton = {
+        _outer: self,
+        label: self._getString("addHandlerAddButton"),
+        accessKey: self._getString("addHandlerAddButtonAccesskey"),
+        feedReaderInfo: { uri: uriSpec, name: aName },
+
+        /* static */
+        callback(aNotification, aButtonInfo) {
+          let uri = aButtonInfo.feedReaderInfo.uri;
+          let name = aButtonInfo.feedReaderInfo.name;
+          let outer = aButtonInfo._outer;
+
+          // The reader could have been added from another window mean while
+          if (!outer.getWebContentHandlerByURI(TYPE_MAYBE_FEED, uri))
+            outer._registerContentHandler(TYPE_MAYBE_FEED, uri, name);
+
+          // avoid reference cycles
+          aButtonInfo._outer = null;
+
+          return false;
+        }
+      };
+      buttons = [addButton];
+    }
+
+    aNotificationBox.appendNotification(message,
+                                        notificationValue,
+                                        notificationIcon,
+                                        aNotificationBox.PRIORITY_INFO_LOW,
+                                        buttons);
+    return true;
+  },
+
+  /**
+   * Save Web Content Handler metadata to persistent preferences.
+   * @param   contentType
+   *          The content Type being handled
+   * @param   uri
+   *          The uri of the web service
+   * @param   title
+   *          The human readable name of the web service
+   *
+   * This data is stored under:
+   *
+   *    browser.contentHandlers.type0 = content/type
+   *    browser.contentHandlers.uri0 = http://www.foo.com/q=%s
+   *    browser.contentHandlers.title0 = Foo 2.0alphr
+   */
+  _saveContentHandlerToPrefs(contentType, uri, title) {
+    let ps = Services.prefs;
+    let i = 0;
+    let typeBranch = null;
+    while (true) {
+      typeBranch =
+        ps.getBranch(PREF_CONTENTHANDLERS_BRANCH + i + ".");
+      try {
+        typeBranch.getCharPref("type");
+        ++i;
+      }
+      catch (e) {
+        // No more handlers
+        break;
+      }
+    }
+    if (typeBranch) {
+      typeBranch.setCharPref("type", contentType);
+      let pls =
+          Cc["@mozilla.org/pref-localizedstring;1"].
+          createInstance(Ci.nsIPrefLocalizedString);
+      pls.data = uri;
+      typeBranch.setComplexValue("uri", Ci.nsIPrefLocalizedString, pls);
+      pls.data = title;
+      typeBranch.setComplexValue("title", Ci.nsIPrefLocalizedString, pls);
+
+      ps.savePrefFile(null);
+    }
+  },
+
+  /**
+   * Determines if there is a type with a particular uri registered for the
+   * specified content type already.
+   * @param   contentType
+   *          The content type that the uri handles
+   * @param   uri
+   *          The uri of the content type
+   */
+  _typeIsRegistered(contentType, uri) {
+    if (!(contentType in this._contentTypes))
+      return false;
+
+    return this._contentTypes[contentType]
+               .some(t => t.uri == uri);
+  },
+
+  /**
+   * Gets a stream converter contract id for the specified content type.
+   * @param   contentType
+   *          The source content type for the conversion.
+   * @returns A contract id to construct a converter to convert between the
+   *          contentType and *\/*.
+   */
+  _getConverterContractID(contentType) {
+    const template = "@mozilla.org/streamconv;1?from=%s&to=*/*";
+    return template.replace(/%s/, contentType);
+  },
+
+  /**
+   * Register a web service handler for a content type.
+   *
+   * @param   contentType
+   *          the content type being handled
+   * @param   uri
+   *          the URI of the web service
+   * @param   title
+   *          the human readable name of the web service
+   */
+  _registerContentHandler(contentType, uri, title) {
+    this._updateContentTypeHandlerMap(contentType, uri, title);
+    this._saveContentHandlerToPrefs(contentType, uri, title);
+
+    if (contentType == TYPE_MAYBE_FEED) {
+      // Make the new handler the last-selected reader in the preview page
+      // and make sure the preview page is shown the next time a feed is visited
+      let pb = Services.prefs.getBranch(null);
+      pb.setCharPref(PREF_SELECTED_READER, "web");
+
+      let supportsString =
+        Cc["@mozilla.org/supports-string;1"].
+        createInstance(Ci.nsISupportsString);
+        supportsString.data = uri;
+      pb.setComplexValue(PREF_SELECTED_WEB, Ci.nsISupportsString,
+                         supportsString);
+      pb.setCharPref(PREF_SELECTED_ACTION, "ask");
+      this._setAutoHandler(TYPE_MAYBE_FEED, null);
+    }
+  },
+
+  /**
+   * Update the content type -> handler map. This mapping is not persisted, use
+   * registerContentHandler or _saveContentHandlerToPrefs for that purpose.
+   * @param   contentType
+   *          The content Type being handled
+   * @param   uri
+   *          The uri of the web service
+   * @param   title
+   *          The human readable name of the web service
+   */
+  _updateContentTypeHandlerMap(contentType, uri, title) {
+    if (!(contentType in this._contentTypes))
+      this._contentTypes[contentType] = [];
+
+    // Avoid adding duplicates
+    if (this._typeIsRegistered(contentType, uri))
+      return;
+
+    this._contentTypes[contentType].push(new ServiceInfo(contentType, uri, title));
+
+    if (!(contentType in this._blockedTypes)) {
+      let converterContractID = this._getConverterContractID(contentType);
+      let cr = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+      cr.registerFactory(WCC_CLASSID, WCC_CLASSNAME, converterContractID,
+                         WebContentConverterFactory);
+    }
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  getContentHandlers(contentType, countRef) {
+    if (countRef) {
+      countRef.value = 0;
+    }
+    if (!(contentType in this._contentTypes))
+      return [];
+
+    let handlers = this._contentTypes[contentType];
+    if (countRef) {
+      countRef.value = handlers.length;
+    }
+    return handlers;
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  resetHandlersForType(contentType) {
+    // currently unused within the tree, so only useful for extensions; previous
+    // impl. was buggy (and even infinite-looped!), so I argue that this is a
+    // definite improvement
+    throw Cr.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  /**
+   * Registers a handler from the settings on a preferences branch.
+   *
+   * Since we support up to six predefined readers, we need to handle gaps
+   * better, since the first branch with user-added values will be .6
+   *
+   * How we deal with that is to check to see if there's no prefs in the
+   * branch and stop cycling once that's true.  This doesn't fix the case
+   * where a user manually removes a reader, but that's not supported yet!
+   *
+   * @param branch
+   *        an nsIPrefBranch containing "type", "uri", and "title" preferences
+   *        corresponding to the content handler to be registered
+   */
+  _registerContentHandlerHavingBranch(branch) {
+    let vals = branch.getChildList("");
+    if (vals.length == 0)
+      return;
+
+    let type = branch.getCharPref("type");
+    let uri = branch.getComplexValue("uri", Ci.nsIPrefLocalizedString).data;
+    let title = branch.getComplexValue("title",
+                                       Ci.nsIPrefLocalizedString).data;
+    this._updateContentTypeHandlerMap(type, uri, title);
+  },
+
+  /**
+   * Load the auto handler, content handler and protocol tables from
+   * preferences.
+   */
+  _init() {
+    let ps = Services.prefs;
+
+    let children = ps.getBranch(PREF_CONTENTHANDLERS_BRANCH)
+                     .getChildList("");
+
+    // first get the numbers of the providers by getting all ###.uri prefs
+    let nums = children.map((child) => {
+      let match = /^(\d+)\.uri$/.exec(child);
+      return match ? match[1] : "";
+    }).filter(child => !!child)
+      .sort();
+
+
+    // now register them
+    for (let num of nums) {
+      let branch = ps.getBranch(PREF_CONTENTHANDLERS_BRANCH + num + ".");
+      try {
+        this._registerContentHandlerHavingBranch(branch);
+      } catch (ex) {
+        // do nothing, the next branch might have values
+      }
+    }
+
+    // We need to do this _after_ registering all of the available handlers,
+    // so that getWebContentHandlerByURI can return successfully.
+    let autoBranch;
+    try {
+      autoBranch = ps.getBranch(PREF_CONTENTHANDLERS_AUTO);
+    } catch (e) {
+      // No auto branch yet, that's fine
+      // LOG("WCCR.init: There is no auto branch, benign");
+    }
+
+    if (autoBranch) {
+      for (let type of autoBranch.getChildList("")) {
+        let uri = autoBranch.getCharPref(type);
+        if (uri) {
+          let handler = this.getWebContentHandlerByURI(type, uri);
+          if (handler) {
+            this._setAutoHandler(type, handler);
+          }
+        }
+      }
+    }
+  },
+
+  /**
+   * See nsIObserver
+   */
+  observe(subject, topic, data) {
+    let os = Services.obs;
+    switch (topic) {
+    case "app-startup":
+      os.addObserver(this, "browser-ui-startup-complete", false);
+      break;
+    case "browser-ui-startup-complete":
+      os.removeObserver(this, "browser-ui-startup-complete");
+      this._init();
+      break;
+    }
+  },
+
+  /**
+   * See nsIFactory
+   */
+  createInstance(outer, iid) {
+    if (outer != null)
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    return this.QueryInterface(iid);
+  },
+
+  classID: WCCR_CLASSID,
+
+  /**
+   * See nsISupports
+   */
+  QueryInterface: XPCOMUtils.generateQI(
+     [Ci.nsIWebContentConverterService,
+      Ci.nsIWebContentHandlerRegistrar,
+      Ci.nsIObserver,
+      Ci.nsIFactory]),
+
+  _xpcom_categories: [{
+    category: "app-startup",
+    service: true
+  }]
+};
+
+function WebContentConverterRegistrarContent() {
+  this._contentTypes = {};
+}
+
+WebContentConverterRegistrarContent.prototype = {
+
+  /**
+   * Load the auto handler, content handler and protocol tables from
+   * preferences.
+   */
+  _init() {
+    let ps = Services.prefs;
+
+    let children = ps.getBranch(PREF_CONTENTHANDLERS_BRANCH)
+                     .getChildList("");
+
+    // first get the numbers of the providers by getting all ###.uri prefs
+    let nums = children.map((child) => {
+      let match = /^(\d+)\.uri$/.exec(child);
+      return match ? match[1] : "";
+    }).filter(child => !!child)
+      .sort();
+
+    // now register them
+    for (num of nums) {
+      let branch = ps.getBranch(PREF_CONTENTHANDLERS_BRANCH + num + ".");
+      try {
+        this._registerContentHandlerHavingBranch(branch);
+      } catch (ex) {
+        // do nothing, the next branch might have values
+      }
+    }
+  },
+
+  _typeIsRegistered(contentType, uri) {
+    return this._contentTypes[contentType]
+               .some(e => e.uri == uri);
+  },
+
+  /**
+   * Since we support up to six predefined readers, we need to handle gaps
+   * better, since the first branch with user-added values will be .6
+   *
+   * How we deal with that is to check to see if there's no prefs in the
+   * branch and stop cycling once that's true.  This doesn't fix the case
+   * where a user manually removes a reader, but that's not supported yet!
+   *
+   * @param   branch
+   *          The pref branch to register the content handler under
+   *
+   */
+  _registerContentHandlerHavingBranch(branch) {
+    let vals = branch.getChildList("");
+    if (vals.length == 0)
+      return;
+
+    let type = branch.getCharPref("type");
+    let uri = branch.getComplexValue("uri", Ci.nsIPrefLocalizedString).data;
+    let title = branch.getComplexValue("title",
+                                       Ci.nsIPrefLocalizedString).data;
+    this._updateContentTypeHandlerMap(type, uri, title);
+  },
+
+  _updateContentTypeHandlerMap(contentType, uri, title) {
+    if (!(contentType in this._contentTypes))
+      this._contentTypes[contentType] = [];
+
+    // Avoid adding duplicates
+    if (this._typeIsRegistered(contentType, uri))
+      return;
+
+    this._contentTypes[contentType].push(new ServiceInfo(contentType, uri, title));
+
+    if (!(contentType in this._blockedTypes)) {
+      let converterContractID = this._getConverterContractID(contentType);
+      let cr = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+      cr.registerFactory(WCC_CLASSID, WCC_CLASSNAME, converterContractID,
+                         WebContentConverterFactory);
+    }
+  },
+
+  /**
+   * See nsIWebContentConverterService
+   */
+  getContentHandlers(contentType, countRef) {
+    this._init();
+    if (countRef) {
+      countRef.value = 0;
+    }
+
+    if (!(contentType in this._contentTypes))
+      return [];
+
+    let handlers = this._contentTypes[contentType];
+    if (countRef) {
+      countRef.value = handlers.length;
+    }
+    return handlers;
+  },
+
+  setAutoHandler(contentType, handler) {
+    Services.cpmm.sendAsyncMessage("WCCR:setAutoHandler",
+                                   { contentType, handler });
+  },
+
+  getWebContentHandlerByURI(contentType, uri) {
+    return this.getContentHandlers(contentType)
+               .find(e => e.uri == uri) || null;
+  },
+
+  /**
+   * See nsIWebContentHandlerRegistrar
+   */
+  registerContentHandler(aContentType, aURIString, aTitle, aBrowserOrWindow) {
+    // aBrowserOrWindow must be a window.
+    let messageManager = aBrowserOrWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                                         .getInterface(Ci.nsIWebNavigation)
+                                         .QueryInterface(Ci.nsIDocShell)
+                                         .QueryInterface(Ci.nsIInterfaceRequestor)
+                                         .getInterface(Ci.nsITabChild)
+                                         .messageManager;
+
+    let uri = Utils.checkAndGetURI(aURIString, aBrowserOrWindow);
+    // XXX We should be throwing a Utils.getSecurityError() here in at least
+    // some cases.  See bug 1266492.
+    if (Utils.resolveContentType(aContentType) != TYPE_MAYBE_FEED) {
+      return;
+    }
+
+    messageManager.sendAsyncMessage("WCCR:registerContentHandler",
+                                    { contentType: aContentType,
+                                      uri: uri.spec,
+                                      title: aTitle });
+  },
+
+  registerProtocolHandler(aProtocol, aURIString, aTitle, aBrowserOrWindow) {
+    // aBrowserOrWindow must be a window.
+    let messageManager = aBrowserOrWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                                         .getInterface(Ci.nsIWebNavigation)
+                                         .QueryInterface(Ci.nsIDocShell)
+                                         .QueryInterface(Ci.nsIInterfaceRequestor)
+                                         .getInterface(Ci.nsITabChild)
+                                         .messageManager;
+
+    let uri = Utils.checkAndGetURI(aURIString, aBrowserOrWindow);
+    Utils.checkProtocolHandlerAllowed(aProtocol, aURIString, aBrowserOrWindow);
+
+    messageManager.sendAsyncMessage("WCCR:registerProtocolHandler",
+                                    { protocol: aProtocol,
+                                      uri: uri.spec,
+                                      title: aTitle });
+  },
+
+  /**
+   * See nsIFactory
+   */
+  createInstance(outer, iid) {
+    if (outer != null)
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    return this.QueryInterface(iid);
+  },
+
+  classID: WCCR_CLASSID,
+
+  /**
+   * See nsISupports
+   */
+  QueryInterface: XPCOMUtils.generateQI(
+                     [Ci.nsIWebContentHandlerRegistrar,
+                      Ci.nsIWebContentConverterService,
+                      Ci.nsIFactory])
+};
+
+this.NSGetFactory =
+  (Services.appinfo.processType === Services.appinfo.PROCESS_TYPE_CONTENT) ?
+    XPCOMUtils.generateNSGetFactory([WebContentConverterRegistrarContent]) :
+    XPCOMUtils.generateNSGetFactory([WebContentConverterRegistrar]);
diff --git a/browser/components/feeds/content/subscribe.js b/browser/components/feeds/content/subscribe.js
new file mode 100644
index 000000000..05a564bf1
--- /dev/null
+++ b/browser/components/feeds/content/subscribe.js
@@ -0,0 +1,25 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* 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/. */
+
+/* global BrowserFeedWriter */
+
+var SubscribeHandler = {
+  /**
+   * The nsIFeedWriter object that produces the UI
+   */
+  _feedWriter: null,
+
+  init: function SH_init() {
+    this._feedWriter = new BrowserFeedWriter();
+  },
+
+  writeContent: function SH_writeContent() {
+    this._feedWriter.writeContent();
+  },
+
+  uninit: function SH_uninit() {
+    this._feedWriter.close();
+  }
+};
diff --git a/browser/components/feeds/content/subscribe.xhtml b/browser/components/feeds/content/subscribe.xhtml
new file mode 100644
index 000000000..a55c80053
--- /dev/null
+++ b/browser/components/feeds/content/subscribe.xhtml
@@ -0,0 +1,74 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- 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/. -->
+
+
+<!DOCTYPE html [
+  <!ENTITY % htmlDTD
+    PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
+    "DTD/xhtml1-strict.dtd">
+  %htmlDTD;
+  <!ENTITY % globalDTD
+    SYSTEM "chrome://global/locale/global.dtd">
+  %globalDTD;
+  <!ENTITY % feedDTD
+    SYSTEM "chrome://browser/locale/feeds/subscribe.dtd">
+  %feedDTD;
+]>
+
+<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
+
+<html id="feedHandler"
+      xmlns="http://www.w3.org/1999/xhtml">
+  <head>
+    <title>&feedPage.title;</title>
+    <link rel="stylesheet"
+          href="chrome://browser/skin/feeds/subscribe.css"
+          type="text/css"
+          media="all"/>
+    <script type="application/javascript"
+            src="chrome://browser/content/feeds/subscribe.js"/>
+  </head>
+  <body onload="SubscribeHandler.writeContent();" onunload="SubscribeHandler.uninit();">
+    <div id="feedHeaderContainer">
+      <div id="feedHeader" dir="&locale.dir;">
+        <div id="feedIntroText">
+          <p id="feedSubscriptionInfo1" />
+          <p id="feedSubscriptionInfo2" />
+        </div>
+        <div id="feedSubscribeLine">
+          <label id="subscribeUsingDescription">
+            <select id="handlersMenuList">
+              <option id="liveBookmarksMenuItem" selected="true">&feedLiveBookmarks;</option>
+              <option disabled="true">&#x2501;&#x2501;&#x2501;&#x2501;&#x2501;&#x2501;&#x2501;</option>
+            </select>
+          </label>
+          <label id="checkboxText">
+            <input type="checkbox" id="alwaysUse" class="alwaysUse" checked="false"/>
+          </label>
+          <button id="subscribeButton">&feedSubscribeNow;</button>
+        </div>
+      </div>
+      <div id="feedHeaderContainerSpacer"/>
+    </div>
+
+    <script type="application/javascript">
+      /* import-globals-from subscribe.js */
+      SubscribeHandler.init();
+    </script>
+
+    <div id="feedBody">
+      <div id="feedTitle">
+        <a id="feedTitleLink">
+          <img id="feedTitleImage"/>
+        </a>
+        <div id="feedTitleContainer">
+          <h1 id="feedTitleText"/>
+          <h2 id="feedSubtitleText"/>
+        </div>
+      </div>
+      <div id="feedContent"/>
+    </div>
+  </body>
+</html>
diff --git a/browser/components/feeds/jar.mn b/browser/components/feeds/jar.mn
new file mode 100644
index 000000000..8570112c1
--- /dev/null
+++ b/browser/components/feeds/jar.mn
@@ -0,0 +1,7 @@
+# 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/.
+
+browser.jar:
+    content/browser/feeds/subscribe.xhtml               (content/subscribe.xhtml) 
+    content/browser/feeds/subscribe.js                  (content/subscribe.js)
diff --git a/browser/components/feeds/moz.build b/browser/components/feeds/moz.build
new file mode 100644
index 000000000..c22129165
--- /dev/null
+++ b/browser/components/feeds/moz.build
@@ -0,0 +1,41 @@
+# -*- 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/.
+
+XPCSHELL_TESTS_MANIFESTS += ['test/unit/xpcshell.ini']
+MOCHITEST_CHROME_MANIFESTS += ['test/chrome/chrome.ini']
+MOCHITEST_MANIFESTS += ['test/mochitest.ini']
+
+JAR_MANIFESTS += ['jar.mn']
+
+XPIDL_SOURCES += [
+    'nsIFeedResultService.idl',
+    'nsIWebContentConverterRegistrar.idl',
+]
+
+XPIDL_MODULE = 'browser-feeds'
+
+SOURCES += [
+    'nsFeedSniffer.cpp',
+]
+
+EXTRA_COMPONENTS += [
+    'BrowserFeeds.manifest',
+    'FeedConverter.js',
+    'FeedWriter.js',
+    'WebContentConverter.js',
+]
+
+FINAL_LIBRARY = 'browsercomps'
+
+for var in ('MOZ_APP_NAME', 'MOZ_MACBUNDLE_NAME'):
+    DEFINES[var] = CONFIG[var]
+
+LOCAL_INCLUDES += [
+    '../build',
+]
+
+with Files('**'):
+    BUG_COMPONENT = ('Firefox', 'RSS Discovery and Preview')
diff --git a/browser/components/feeds/nsFeedSniffer.cpp b/browser/components/feeds/nsFeedSniffer.cpp
new file mode 100644
index 000000000..f2d0da776
--- /dev/null
+++ b/browser/components/feeds/nsFeedSniffer.cpp
@@ -0,0 +1,370 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "nsFeedSniffer.h"
+
+
+#include "nsNetCID.h"
+#include "nsXPCOM.h"
+#include "nsCOMPtr.h"
+#include "nsStringStream.h"
+
+#include "nsBrowserCompsCID.h"
+
+#include "nsICategoryManager.h"
+#include "nsIServiceManager.h"
+#include "nsComponentManagerUtils.h"
+#include "nsServiceManagerUtils.h"
+
+#include "nsIStreamConverterService.h"
+#include "nsIStreamConverter.h"
+
+#include "nsIStreamListener.h"
+
+#include "nsIHttpChannel.h"
+#include "nsIMIMEHeaderParam.h"
+
+#include "nsMimeTypes.h"
+#include "nsIURI.h"
+#include <algorithm>
+
+#define TYPE_ATOM "application/atom+xml"
+#define TYPE_RSS "application/rss+xml"
+#define TYPE_MAYBE_FEED "application/vnd.mozilla.maybe.feed"
+
+#define NS_RDF "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+#define NS_RSS "http://purl.org/rss/1.0/"
+
+#define MAX_BYTES 512u
+
+NS_IMPL_ISUPPORTS(nsFeedSniffer,
+                  nsIContentSniffer,
+                  nsIStreamListener,
+                  nsIRequestObserver)
+
+nsresult
+nsFeedSniffer::ConvertEncodedData(nsIRequest* request,
+                                  const uint8_t* data,
+                                  uint32_t length)
+{
+  nsresult rv = NS_OK;
+
+ mDecodedData = "";
+ nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(request));
+  if (!httpChannel)
+    return NS_ERROR_NO_INTERFACE;
+
+  nsAutoCString contentEncoding;
+  httpChannel->GetResponseHeader(NS_LITERAL_CSTRING("Content-Encoding"), 
+                                 contentEncoding);
+  if (!contentEncoding.IsEmpty()) {
+    nsCOMPtr<nsIStreamConverterService> converterService(do_GetService(NS_STREAMCONVERTERSERVICE_CONTRACTID));
+    if (converterService) {
+      ToLowerCase(contentEncoding);
+
+      nsCOMPtr<nsIStreamListener> converter;
+      rv = converterService->AsyncConvertData(contentEncoding.get(), 
+                                              "uncompressed", this, nullptr, 
+                                              getter_AddRefs(converter));
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      converter->OnStartRequest(request, nullptr);
+
+      nsCOMPtr<nsIStringInputStream> rawStream =
+        do_CreateInstance(NS_STRINGINPUTSTREAM_CONTRACTID);
+      if (!rawStream)
+        return NS_ERROR_FAILURE;
+
+      rv = rawStream->SetData((const char*)data, length);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      rv = converter->OnDataAvailable(request, nullptr, rawStream, 0, length);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      converter->OnStopRequest(request, nullptr, NS_OK);
+    }
+  }
+  return rv;
+}
+
+template<int N>
+static bool
+StringBeginsWithLowercaseLiteral(nsAString& aString,
+                                 const char (&aSubstring)[N])
+{
+  return StringHead(aString, N).LowerCaseEqualsLiteral(aSubstring);
+}
+
+bool
+HasAttachmentDisposition(nsIHttpChannel* httpChannel)
+{
+  if (!httpChannel)
+    return false;
+
+  uint32_t disp;
+  nsresult rv = httpChannel->GetContentDisposition(&disp);
+
+  if (NS_SUCCEEDED(rv) && disp == nsIChannel::DISPOSITION_ATTACHMENT)
+    return true;
+
+  return false;
+}
+
+/**
+ * @return the first occurrence of a character within a string buffer,
+ *         or nullptr if not found
+ */
+static const char*
+FindChar(char c, const char *begin, const char *end)
+{
+  for (; begin < end; ++begin) {
+    if (*begin == c)
+      return begin;
+  }
+  return nullptr;
+}
+
+/**
+ *
+ * Determine if a substring is the "documentElement" in the document.
+ *
+ * All of our sniffed substrings: <rss, <feed, <rdf:RDF must be the "document"
+ * element within the XML DOM, i.e. the root container element. Otherwise,
+ * it's possible that someone embedded one of these tags inside a document of
+ * another type, e.g. a HTML document, and we don't want to show the preview
+ * page if the document isn't actually a feed.
+ *
+ * @param   start
+ *          The beginning of the data being sniffed
+ * @param   end
+ *          The end of the data being sniffed, right before the substring that
+ *          was found.
+ * @returns true if the found substring is the documentElement, false 
+ *          otherwise.
+ */
+static bool
+IsDocumentElement(const char *start, const char* end)
+{
+  // For every tag in the buffer, check to see if it's a PI, Doctype or 
+  // comment, our desired substring or something invalid.
+  while ( (start = FindChar('<', start, end)) ) {
+    ++start;
+    if (start >= end)
+      return false;
+
+    // Check to see if the character following the '<' is either '?' or '!'
+    // (processing instruction or doctype or comment)... these are valid nodes
+    // to have in the prologue. 
+    if (*start != '?' && *start != '!')
+      return false;
+    
+    // Now advance the iterator until the '>' (We do this because we don't want
+    // to sniff indicator substrings that are embedded within other nodes, e.g.
+    // comments: <!-- <rdf:RDF .. > -->
+    start = FindChar('>', start, end);
+    if (!start)
+      return false;
+
+    ++start;
+  }
+  return true;
+}
+
+/**
+ * Determines whether or not a string exists as the root element in an XML data
+ * string buffer.
+ * @param   dataString
+ *          The data being sniffed
+ * @param   substring
+ *          The substring being tested for existence and root-ness.
+ * @returns true if the substring exists and is the documentElement, false
+ *          otherwise.
+ */
+static bool
+ContainsTopLevelSubstring(nsACString& dataString, const char *substring) 
+{
+  nsACString::const_iterator start, end;
+  dataString.BeginReading(start);
+  dataString.EndReading(end);
+
+  if (!FindInReadable(nsCString(substring), start, end)){
+    return false;
+  }
+
+  auto offset = start.get() - dataString.Data();
+
+  const char *begin = dataString.BeginReading();
+
+  // Only do the validation when we find the substring.
+  return IsDocumentElement(begin, begin + offset);
+}
+
+NS_IMETHODIMP
+nsFeedSniffer::GetMIMETypeFromContent(nsIRequest* request, 
+                                      const uint8_t* data, 
+                                      uint32_t length, 
+                                      nsACString& sniffedType)
+{
+  nsCOMPtr<nsIHttpChannel> channel(do_QueryInterface(request));
+  if (!channel)
+    return NS_ERROR_NO_INTERFACE;
+
+  // Check that this is a GET request, since you can't subscribe to a POST...
+  nsAutoCString method;
+  channel->GetRequestMethod(method);
+  if (!method.EqualsLiteral("GET")) {
+    sniffedType.Truncate();
+    return NS_OK;
+  }
+
+  // We need to find out if this is a load of a view-source document. In this
+  // case we do not want to override the content type, since the source display
+  // does not need to be converted from feed format to XUL. More importantly, 
+  // we don't want to change the content type from something 
+  // nsContentDLF::CreateInstance knows about (e.g. application/xml, text/html 
+  // etc) to something that only the application fe knows about (maybe.feed) 
+  // thus deactivating syntax highlighting.
+  nsCOMPtr<nsIURI> originalURI;
+  channel->GetOriginalURI(getter_AddRefs(originalURI));
+
+  nsAutoCString scheme;
+  originalURI->GetScheme(scheme);
+  if (scheme.EqualsLiteral("view-source")) {
+    sniffedType.Truncate();
+    return NS_OK;
+  }
+
+  // Check the Content-Type to see if it is set correctly. If it is set to 
+  // something specific that we think is a reliable indication of a feed, don't
+  // bother sniffing since we assume the site maintainer knows what they're 
+  // doing. 
+  nsAutoCString contentType;
+  channel->GetContentType(contentType);
+  bool noSniff = contentType.EqualsLiteral(TYPE_RSS) ||
+                   contentType.EqualsLiteral(TYPE_ATOM);
+
+  // Check to see if this was a feed request from the location bar or from
+  // the feed: protocol. This is also a reliable indication.
+  // The value of the header doesn't matter.  
+  if (!noSniff) {
+    nsAutoCString sniffHeader;
+    nsresult foundHeader =
+      channel->GetRequestHeader(NS_LITERAL_CSTRING("X-Moz-Is-Feed"),
+                                sniffHeader);
+    noSniff = NS_SUCCEEDED(foundHeader);
+  }
+
+  if (noSniff) {
+    // check for an attachment after we have a likely feed.
+    if(HasAttachmentDisposition(channel)) {
+      sniffedType.Truncate();
+      return NS_OK;
+    }
+
+    // set the feed header as a response header, since we have good metadata
+    // telling us that the feed is supposed to be RSS or Atom
+    channel->SetResponseHeader(NS_LITERAL_CSTRING("X-Moz-Is-Feed"),
+                               NS_LITERAL_CSTRING("1"), false);
+    sniffedType.AssignLiteral(TYPE_MAYBE_FEED);
+    return NS_OK;
+  }
+
+  // Don't sniff arbitrary types.  Limit sniffing to situations that
+  // we think can reasonably arise.
+  if (!contentType.EqualsLiteral(TEXT_HTML) &&
+      !contentType.EqualsLiteral(APPLICATION_OCTET_STREAM) &&
+      // Same criterion as XMLHttpRequest.  Should we be checking for "+xml"
+      // and check for text/xml and application/xml by hand instead?
+      contentType.Find("xml") == -1) {
+    sniffedType.Truncate();
+    return NS_OK;
+  }
+
+  // Now we need to potentially decompress data served with 
+  // Content-Encoding: gzip
+  nsresult rv = ConvertEncodedData(request, data, length);
+  if (NS_FAILED(rv))
+    return rv;
+
+  // We cap the number of bytes to scan at MAX_BYTES to prevent picking up 
+  // false positives by accidentally reading document content, e.g. a "how to
+  // make a feed" page.
+  const char* testData;
+  if (mDecodedData.IsEmpty()) {
+    testData = (const char*)data;
+    length = std::min(length, MAX_BYTES);
+  } else {
+    testData = mDecodedData.get();
+    length = std::min(mDecodedData.Length(), MAX_BYTES);
+  }
+
+  // The strategy here is based on that described in:
+  // http://blogs.msdn.com/rssteam/articles/PublishersGuide.aspx
+  // for interoperarbility purposes.
+
+  // Thus begins the actual sniffing.
+  nsDependentCSubstring dataString((const char*)testData, length);
+
+  bool isFeed = false;
+
+  // RSS 0.91/0.92/2.0
+  isFeed = ContainsTopLevelSubstring(dataString, "<rss");
+
+  // Atom 1.0
+  if (!isFeed)
+    isFeed = ContainsTopLevelSubstring(dataString, "<feed");
+
+  // RSS 1.0
+  if (!isFeed) {
+    bool foundNS_RDF = FindInReadable(NS_LITERAL_CSTRING(NS_RDF), dataString);
+    bool foundNS_RSS = FindInReadable(NS_LITERAL_CSTRING(NS_RSS), dataString);
+    isFeed = ContainsTopLevelSubstring(dataString, "<rdf:RDF") &&
+      foundNS_RDF && foundNS_RSS;
+  }
+
+  // If we sniffed a feed, coerce our internal type
+  if (isFeed && !HasAttachmentDisposition(channel))
+    sniffedType.AssignLiteral(TYPE_MAYBE_FEED);
+  else
+    sniffedType.Truncate();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsFeedSniffer::OnStartRequest(nsIRequest* request, nsISupports* context)
+{
+  return NS_OK;
+}
+
+nsresult
+nsFeedSniffer::AppendSegmentToString(nsIInputStream* inputStream,
+                                     void* closure,
+                                     const char* rawSegment,
+                                     uint32_t toOffset,
+                                     uint32_t count,
+                                     uint32_t* writeCount)
+{
+  nsCString* decodedData = static_cast<nsCString*>(closure);
+  decodedData->Append(rawSegment, count);
+  *writeCount = count;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsFeedSniffer::OnDataAvailable(nsIRequest* request, nsISupports* context,
+                               nsIInputStream* stream, uint64_t offset, 
+                               uint32_t count)
+{
+  uint32_t read;
+  return stream->ReadSegments(AppendSegmentToString, &mDecodedData, count, 
+                              &read);
+}
+
+NS_IMETHODIMP
+nsFeedSniffer::OnStopRequest(nsIRequest* request, nsISupports* context, 
+                             nsresult status)
+{
+  return NS_OK; 
+}
diff --git a/browser/components/feeds/nsFeedSniffer.h b/browser/components/feeds/nsFeedSniffer.h
new file mode 100644
index 000000000..b7ac002bd
--- /dev/null
+++ b/browser/components/feeds/nsFeedSniffer.h
@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+
+#include "nsIContentSniffer.h"
+#include "nsIStreamListener.h"
+#include "nsString.h"
+#include "mozilla/Attributes.h"
+
+class nsFeedSniffer final : public nsIContentSniffer,
+                                   nsIStreamListener
+{
+public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSICONTENTSNIFFER
+  NS_DECL_NSIREQUESTOBSERVER
+  NS_DECL_NSISTREAMLISTENER
+
+  static nsresult AppendSegmentToString(nsIInputStream* inputStream,
+                                        void* closure,
+                                        const char* rawSegment,
+                                        uint32_t toOffset,
+                                        uint32_t count,
+                                        uint32_t* writeCount);
+
+protected:
+  ~nsFeedSniffer() {}
+
+  nsresult ConvertEncodedData(nsIRequest* request, const uint8_t* data,
+                              uint32_t length);
+
+private:
+  nsCString mDecodedData;
+};
+
diff --git a/browser/components/feeds/nsIFeedResultService.idl b/browser/components/feeds/nsIFeedResultService.idl
new file mode 100644
index 000000000..f745fa693
--- /dev/null
+++ b/browser/components/feeds/nsIFeedResultService.idl
@@ -0,0 +1,70 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "nsISupports.idl"
+interface nsIURI;
+interface nsIRequest;
+interface nsIFeedResult;
+
+/**
+ * nsIFeedResultService provides a globally-accessible object for retrieving
+ * the results of feed processing.
+ */
+[scriptable, uuid(95309fd2-7b3a-47fb-97f3-5c460d9473cd)]
+interface nsIFeedResultService : nsISupports
+{
+  /**
+   * When set to true, forces the preview page to be displayed, regardless
+   * of the user's preferences.
+   */
+  attribute boolean forcePreviewPage;
+
+  /**
+   * Adds a URI to the user's specified external feed handler, or live
+   * bookmarks.
+   * @param   uri
+   *          The uri of the feed to add.
+   * @param   title
+   *          The title of the feed to add.
+   * @param   subtitle
+   *          The subtitle of the feed to add.
+   * @param   feedType
+   *          The nsIFeed type of the feed.  See nsIFeed.idl
+   * @param   feedReader
+   *          The type of feed reader we're using (client, bookmarks, default)
+   *          If this parameter is null, the type is set to default
+   */
+  void addToClientReader(in AUTF8String uri,
+                         in AString title,
+                         in AString subtitle,
+                         in unsigned long feedType,
+                         [optional] in AString feedReader);
+
+  /**
+   * Registers a Feed Result object with a globally accessible service
+   * so that it can be accessed by a singleton method outside the usual
+   * flow of control in document loading.
+   *
+   * @param   feedResult
+   *          An object implementing nsIFeedResult representing the feed.
+   */
+  void addFeedResult(in nsIFeedResult feedResult);
+
+  /**
+   * Gets a Feed Handler object registered using addFeedResult.
+   *
+   * @param   uri
+   *          The URI of the feed a handler is being requested for
+   */
+  nsIFeedResult getFeedResult(in nsIURI uri);
+
+  /**
+   * Unregisters a Feed Handler object registered using addFeedResult.
+   * @param   uri
+   *          The feed URI the handler was registered under. This must be
+   *          the same *instance* the feed was registered under.
+   */
+  void removeFeedResult(in nsIURI uri);
+};
diff --git a/browser/components/feeds/nsIWebContentConverterRegistrar.idl b/browser/components/feeds/nsIWebContentConverterRegistrar.idl
new file mode 100644
index 000000000..08ce2f4ae
--- /dev/null
+++ b/browser/components/feeds/nsIWebContentConverterRegistrar.idl
@@ -0,0 +1,117 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "nsIMIMEInfo.idl"
+#include "nsIWebContentHandlerRegistrar.idl"
+
+interface nsIRequest;
+
+[scriptable, uuid(eb361098-5158-4b21-8f98-50b445f1f0b2)]
+interface nsIWebContentHandlerInfo : nsIHandlerApp
+{
+  /**
+   * The content type handled by the handler
+   */
+  readonly attribute AString contentType;
+
+  /**
+   * The uri of the handler, with an embedded %s where the URI of the loaded
+   * document will be encoded.
+   */
+  readonly attribute AString uri;
+
+  /** 
+   * Gets the service URL Spec, with the loading document URI encoded in it.
+   * @param   uri
+   *          The URI of the document being loaded
+   * @returns The URI of the service with the loading document URI encoded in 
+   *          it.
+   */
+  AString getHandlerURI(in AString uri);
+};
+
+[scriptable, uuid(de7cc06e-e778-45cb-b7db-7a114e1e75b1)]
+interface nsIWebContentConverterService : nsIWebContentHandlerRegistrar
+{
+  /**
+   * Specifies the handler to be used to automatically handle all links of a
+   * certain content type from now on. 
+   * @param   contentType
+   *          The content type to automatically load with the specified handler
+   * @param   handler
+   *          A web service handler. If this is null, no automatic action is
+   *          performed and the user must choose.
+   * @throws  NS_ERROR_NOT_AVAILABLE if the service refered to by |handler| is 
+   *          not already registered.
+   */
+  void setAutoHandler(in AString contentType, in nsIWebContentHandlerInfo handler);
+
+  /**
+   * Gets the auto handler specified for a particular content type
+   * @param   contentType
+   *          The content type to look up an auto handler for.
+   * @returns The web service handler that will automatically handle all 
+   *          documents of the specified type. null if there is no automatic
+   *          handler. (Handlers may be registered, just none of them specified
+   *          as "automatic").
+   */
+  nsIWebContentHandlerInfo getAutoHandler(in AString contentType);
+
+  /**
+   * Gets a web handler for the specified service URI
+   * @param   contentType
+   *          The content type of the service being located
+   * @param   uri
+   *          The service URI of the handler to locate.
+   * @returns A web service handler that uses the specified uri.
+   */
+  nsIWebContentHandlerInfo getWebContentHandlerByURI(in AString contentType, 
+                                                     in AString uri);
+
+  /**
+   * Loads the preferred handler when content of a registered type is about
+   * to be loaded.
+   * @param   request
+   *          The nsIRequest for the load of the content
+   */
+  void loadPreferredHandler(in nsIRequest request);
+
+  /**
+   * Removes a registered protocol handler
+   * @param   protocol
+   *          The protocol scheme to remove a service handler for
+   * @param   uri
+   *          The uri of the service handler to remove
+   */
+  void removeProtocolHandler(in AString protocol, in AString uri);
+
+  /**
+   * Removes a registered content handler
+   * @param   contentType
+   *          The content type to remove a service handler for
+   * @param   uri
+   *          The uri of the service handler to remove
+   */
+  void removeContentHandler(in AString contentType, in AString uri);
+
+  /**
+   * Gets the list of content handlers for a particular type.
+   * @param   contentType
+   *          The content type to get handlers for
+   * @returns An array of nsIWebContentHandlerInfo objects
+   */
+  void getContentHandlers(in AString contentType,
+                          [optional] out unsigned long count,
+                          [retval,array,size_is(count)] out nsIWebContentHandlerInfo handlers);
+
+  /**
+   * Resets the list of available content handlers to the default set from
+   * the distribution.
+   * @param   contentType
+   *          The content type to reset handlers for
+   */
+  void resetHandlersForType(in AString contentType);
+};
+
diff --git a/browser/components/feeds/test/.eslintrc.js b/browser/components/feeds/test/.eslintrc.js
new file mode 100644
index 000000000..3c788d6d6
--- /dev/null
+++ b/browser/components/feeds/test/.eslintrc.js
@@ -0,0 +1,7 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "../../../../testing/mochitest/mochitest.eslintrc.js"
+  ]
+};
diff --git a/browser/components/feeds/test/bug368464-data.xml b/browser/components/feeds/test/bug368464-data.xml
new file mode 100644
index 000000000..2745b061d
--- /dev/null
+++ b/browser/components/feeds/test/bug368464-data.xml
@@ -0,0 +1,18 @@
+<?xml version="1.0"?>
+                 <rdf:RDF 
+               xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+               xmlns="http://my.netscape.com/rdf/simple/0.9/">
+               <channel>
+               <title>Tinderbox - Firefox</title>
+               <description>Build bustages for Firefox</description>
+               <link>http://tinderbox.mozilla.org/showbuilds.cgi?tree=Firefox</link>
+               </channel>
+               <image>
+               <title>Bad</title>
+               <url>http://tinderbox.mozilla.org/channelflames.gif</url>
+               <link>http://tinderbox.mozilla.org/showbuilds.cgi?tree=Firefox</link>
+               </image>
+           <item><title>The tree is currently closed</title><link>http://tinderbox.mozilla.org/showbuilds.cgi?tree=Firefox</link></item>
+
+<item><title>MacOSX Darwin 8.8.4 qm-xserve01 dep unit test is in flames</title><link>http://tinderbox.mozilla.org/showbuilds.cgi?tree=Firefox</link></item>
+</rdf:RDF>
diff --git a/browser/components/feeds/test/bug408328-data.xml b/browser/components/feeds/test/bug408328-data.xml
new file mode 100644
index 000000000..e9385e5ab
--- /dev/null
+++ b/browser/components/feeds/test/bug408328-data.xml
@@ -0,0 +1,63 @@
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+
+  <title>Example Feed</title> 
+  <link href="http://example.org/"/>
+  <updated>2003-12-13T18:30:02Z</updated>
+
+  <author> 
+    <name>John Doe</name>
+  </author> 
+  <id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>
+
+  <entry>
+
+    <title>Good item</title>
+    <link href="http://example.org/first"/>
+    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
+    <updated>2003-12-13T18:30:02Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+  <entry>
+
+    <title>data: link</title>
+    <link href="data:text/plain,Hi"/>
+    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6b</id>
+    <updated>2003-12-13T18:30:03Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+  
+  <entry>
+
+    <title>javascript: link</title>
+    <link href="javascript:alert('Hi')"/>
+    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6c</id>
+    <updated>2003-12-13T18:30:04Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+  
+  <entry>
+
+    <title>file: link</title>
+    <link href="file:///var/"/>
+    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6d</id>
+    <updated>2003-12-13T18:30:05Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+  <entry>
+
+    <title>chrome: link</title>
+    <link href="chrome://browser/content/browser.js"/>
+    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6e</id>
+    <updated>2003-12-13T18:30:06Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>
diff --git a/browser/components/feeds/test/bug436801-data.xml b/browser/components/feeds/test/bug436801-data.xml
new file mode 100644
index 000000000..0e45c7ed8
--- /dev/null
+++ b/browser/components/feeds/test/bug436801-data.xml
@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom" xml:base="http://www.example.com/">
+
+  <title type="xhtml" xml:base="/foo/bar/">
+    <div xmlns="http://www.w3.org/1999/xhtml">Example of a <em>special</em> feed (<img height="20px" src="baz.png" alt="base test sprite"/>)</div>
+  </title>
+
+  <subtitle type="html" xml:base="/foo/bar/">
+    <![CDATA[
+      With a <em>special</em> subtitle (<img height="20px" src="baz.png" alt="base test sprite"/>)
+    ]]>
+  </subtitle>
+
+  <link href="http://example.org/"/>
+
+  <updated>2010-09-02T18:30:02Z</updated>
+
+  <author>
+    <name>John Doe</name>
+  </author>
+
+  <id>urn:uuid:22906062-ecbd-46e2-b6a7-3039506a398f</id>
+
+  <entry>
+    <title type="xhtml" xml:base="/foo/bar/">
+      <div xmlns="http://www.w3.org/1999/xhtml">Some <abbr title="Extensible Hyper-text Mark-up Language">XHTML</abbr> examples (<img height="20px" src="baz.png" alt="base test sprite"/>)</div>
+    </title>
+    <id>urn:uuid:b48083a7-71a7-4c9c-8515-b7c0d22955e7</id>
+    <updated>2010-09-02T18:30:02Z</updated>
+    <summary>Some text.</summary>
+  </entry>
+
+  <entry>
+    <title type="html" xml:base="/foo/bar/">
+      <![CDATA[
+        Some <abbr title="Hyper-text Mark-up Language">HTML</abbr> examples (<img height="20px" src="baz.png" alt="base test sprite"/>)
+      ]]>
+    </title>
+    <id>urn:uuid:1424967a-280a-414d-b0ab-8b11c4ac1bb7</id>
+    <updated>2010-09-02T18:30:02Z</updated>
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>
diff --git a/browser/components/feeds/test/bug494328-data.xml b/browser/components/feeds/test/bug494328-data.xml
new file mode 100644
index 000000000..58342bafc
--- /dev/null
+++ b/browser/components/feeds/test/bug494328-data.xml
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>

+<rss version="2.0">

+  <channel>

+    <title>Channel title</title>

+    <description>Channel description</description>

+    <link>Channel link</link>

+    <item>

+      <title>Episode 1</title>

+      <enclosure url="http://www.example.com/podcasts/Episode%201" length="0" type="audio/x-m4a" />

+    </item>

+    <item>

+      <title>Episode 2</title>

+      <enclosure url="http://www.example.com/podcasts/Episode%20%232" length="0" type="audio/x-m4a" />

+    </item>

+    <item>

+      <title>Episode 3</title>

+      <enclosure url="http://www.example.com/podcasts/Episode%20%233/" length="0" type="audio/x-m4a" />

+    </item>

+    <item>

+      <title>Episode 4</title>

+      <enclosure url="http://www.example.com/podcasts/Is%20This%20Episode%20%234%3F" length="0" type="audio/x-m4a" />

+    </item>

+  </channel>

+</rss>

diff --git a/browser/components/feeds/test/bug589543-data.xml b/browser/components/feeds/test/bug589543-data.xml
new file mode 100644
index 000000000..0e700b6d8
--- /dev/null
+++ b/browser/components/feeds/test/bug589543-data.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+
+  <title>Example Feed</title>
+  <link href="http://example.org/"/>
+  <updated>2010-08-22T18:30:02Z</updated>
+
+  <author>
+    <name>John Doe</name>
+  </author>
+  <id>urn:uuid:e2df8375-99be-4848-b05e-b9d407555267</id>
+
+  <entry>
+
+    <title>Item</title>
+    <link href="http://example.org/first"/>
+    <id>urn:uuid:9e0f4bed-33d3-4a9d-97ab-ecaa31b3f14a</id>
+    <updated>2010-08-22T18:30:02Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>
diff --git a/browser/components/feeds/test/chrome/.eslintrc.js b/browser/components/feeds/test/chrome/.eslintrc.js
new file mode 100644
index 000000000..8c0f4f574
--- /dev/null
+++ b/browser/components/feeds/test/chrome/.eslintrc.js
@@ -0,0 +1,7 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "../../../../../testing/mochitest/chrome.eslintrc.js"
+  ]
+};
diff --git a/browser/components/feeds/test/chrome/chrome.ini b/browser/components/feeds/test/chrome/chrome.ini
new file mode 100644
index 000000000..7bad142ab
--- /dev/null
+++ b/browser/components/feeds/test/chrome/chrome.ini
@@ -0,0 +1,10 @@
+[DEFAULT]
+support-files = sample_feed.atom
+  !/browser/components/feeds/test/bug408328-data.xml
+  !/browser/components/feeds/test/valid-feed.xml
+  !/browser/components/feeds/test/valid-unsniffable-feed.xml
+
+[test_423060.xul]
+[test_bug368464.html]
+[test_bug408328.html]
+[test_maxSniffing.html]
diff --git a/browser/components/feeds/test/chrome/sample_feed.atom b/browser/components/feeds/test/chrome/sample_feed.atom
new file mode 100644
index 000000000..add75efb4
--- /dev/null
+++ b/browser/components/feeds/test/chrome/sample_feed.atom
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+
+  <title>Example Feed</title> 
+  <link href="http://example.org/"/>
+  <updated>2003-12-13T18:30:02Z</updated>
+
+  <author> 
+    <name>John Doe</name>
+  </author> 
+  <id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>
+
+  <entry>
+
+    <title>Atom-Powered Robots Run Amok</title>
+    <link href="http://example.org/2003/12/13/atom03"/>
+    <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
+    <updated>2003-12-13T18:30:02Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>
diff --git a/browser/components/feeds/test/chrome/test_423060.xul b/browser/components/feeds/test/chrome/test_423060.xul
new file mode 100644
index 000000000..465cf2dd2
--- /dev/null
+++ b/browser/components/feeds/test/chrome/test_423060.xul
@@ -0,0 +1,56 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+<?xml-stylesheet
+  href="chrome://mochikit/content/tests/SimpleTest/test.css" type="text/css"?>
+<window title="Make sure feed preview works when a default reader is selected"
+  xmlns:html="http://www.w3.org/1999/xhtml"
+  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script type="application/javascript"
+   src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+
+  <body xmlns="http://www.w3.org/1999/xhtml" />
+
+  <script type="application/javascript">
+    SimpleTest.waitForExplicitFinish();
+
+    const Cc = Components.classes;
+    const Ci = Components.interfaces;
+
+    var wccrID = "@mozilla.org/embeddor.implemented/web-content-handler-registrar;1";
+    /* abort the test if web feed handlers are not available */
+    if (!Cc[wccrID])
+      SimpleTest.finish()
+
+    /* Turn off the first run UI */
+    var prefBranch = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
+    prefBranch.setBoolPref("browser.feeds.showFirstRunUI", false);
+
+    /* register a handler for the feed type */
+    const MAYBE_FEED = "application/vnd.mozilla.maybe.feed";
+    var handlerPage = "http://mochi.test:8888/tests/toolkit/components/places/tests/chrome/demohandler.html?feedurl=%s";
+    var wccr = Cc[wccrID].getService(Ci.nsIWebContentConverterService);
+    wccr.registerContentHandler(MAYBE_FEED, handlerPage, "Demo handler", null);
+    var demoHandler = wccr.getWebContentHandlerByURI(MAYBE_FEED, handlerPage);
+    wccr.setAutoHandler(MAYBE_FEED, demoHandler);
+
+    /* Don't show the preview page */
+    prefBranch.setCharPref("browser.feeds.handler", "reader");
+
+    function finishUp() {
+      var theframe = document.getElementById('theframe');
+      var previewURL = "http://mochi.test:8888/tests/toolkit/components/places/tests/chrome/demohandler.html?feedurl=http%3A%2F%2Fmochi.test%3A8888%2Ftests%2Ftoolkit%2Fcomponents%2Fplaces%2Ftests%2Fchrome%2Fsample_feed.atom";
+      is(theframe.contentDocument.URL, previewURL);
+
+      /* remove our demoHandler */
+      wccr.setAutoHandler(MAYBE_FEED, null);
+      wccr.removeContentHandler(MAYBE_FEED, handlerPage);
+      prefBranch.setCharPref("browser.feeds.handler", "ask");
+      prefBranch.setBoolPref("browser.feeds.showFirstRunUI", true);
+
+      SimpleTest.finish();
+    }
+  </script>
+  <html:iframe src="http://mochi.test:8888/tests/toolkit/components/places/tests/chrome/sample_feed.atom" height="400px" 
+    id="theframe" onload="finishUp();">
+  </html:iframe>
+</window>
diff --git a/browser/components/feeds/test/chrome/test_bug368464.html b/browser/components/feeds/test/chrome/test_bug368464.html
new file mode 100644
index 000000000..dd7486f66
--- /dev/null
+++ b/browser/components/feeds/test/chrome/test_bug368464.html
@@ -0,0 +1,32 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=368464
+-->
+<head>
+  <title>Test that RSS 0.90 isn't sniffed</title>
+  <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=368464">Mozilla Bug 368464</a>
+<p id="display"><iframe id="testFrame" src="http://mochi.test:8888/tests/browser/components/feeds/test/bug368464-data.xml"></iframe></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 368464 **/
+SimpleTest.waitForExplicitFinish();
+
+addLoadEvent(function() {
+  ok($("testFrame").contentDocument.documentElement.id != "feedHandler",
+     "RSS 0.90 shouldn't be sniffed as a feed");
+});
+addLoadEvent(SimpleTest.finish);
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/browser/components/feeds/test/chrome/test_bug408328.html b/browser/components/feeds/test/chrome/test_bug408328.html
new file mode 100644
index 000000000..e4901320a
--- /dev/null
+++ b/browser/components/feeds/test/chrome/test_bug408328.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=408328
+-->
+<head>
+  <title>Test feed preview safe-linkification</title>
+  <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=408328">Mozilla Bug 408328</a>
+<p id="display"><iframe id="testFrame" src="http://mochi.test:8888/tests/browser/components/feeds/test/bug408328-data.xml"></iframe></p>
+<div id="content" style="display: none">
+  
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 408328 **/
+SimpleTest.waitForExplicitFinish();
+
+addLoadEvent(function() {
+  var links = $("testFrame").contentDocument.getElementById("feedContent").getElementsByTagName("a");
+  is(links.length, 5, "wrong number of linked items in feed preview");
+  for (var i = 0; i < links.length; i++) {
+    if (links[i].href)
+      is(links[i].href, "http://example.org/first", "bad linkified item");
+  }
+});
+addLoadEvent(SimpleTest.finish);
+
+</script>
+</pre>
+</body>
+</html>
+
diff --git a/browser/components/feeds/test/chrome/test_maxSniffing.html b/browser/components/feeds/test/chrome/test_maxSniffing.html
new file mode 100644
index 000000000..7a2044687
--- /dev/null
+++ b/browser/components/feeds/test/chrome/test_maxSniffing.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=739040
+-->
+<head>
+  <title>Test that we only sniff 512 bytes</title>
+  <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=739040">Mozilla Bug 739040</a>
+<p id="display">
+  <iframe id="validTestFrame" src="http://mochi.test:8888/tests/browser/components/feeds/test/valid-feed.xml"></iframe>
+  <iframe id="unsniffableTestFrame" src="http://mochi.test:8888/tests/browser/components/feeds/test/valid-unsniffable-feed.xml"></iframe>
+</p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 739040 **/
+SimpleTest.waitForExplicitFinish();
+
+addLoadEvent(function() {
+  is($("validTestFrame").contentDocument.documentElement.id, "feedHandler",
+     "valid feed should be sniffed");
+  isnot($("unsniffableTestFrame").contentDocument.documentElement.id, "feedHandler",
+        "unsniffable feed should not be sniffed");
+});
+addLoadEvent(SimpleTest.finish);
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/browser/components/feeds/test/mochitest.ini b/browser/components/feeds/test/mochitest.ini
new file mode 100644
index 000000000..fc1e6a1a9
--- /dev/null
+++ b/browser/components/feeds/test/mochitest.ini
@@ -0,0 +1,14 @@
+[DEFAULT]
+support-files =
+  bug368464-data.xml
+  bug408328-data.xml
+  bug436801-data.xml
+  bug494328-data.xml
+  bug589543-data.xml
+  valid-feed.xml
+  valid-unsniffable-feed.xml
+
+[test_bug436801.html]
+[test_bug494328.html]
+[test_bug589543.html]
+[test_registerHandler.html]
diff --git a/browser/components/feeds/test/test_bug436801.html b/browser/components/feeds/test/test_bug436801.html
new file mode 100644
index 000000000..29fb5acf0
--- /dev/null
+++ b/browser/components/feeds/test/test_bug436801.html
@@ -0,0 +1,118 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=436801
+-->
+<head>
+  <title>Test feed preview subscribe UI</title>
+  <script type="text/javascript" src="/MochiKit/packed.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=436801">Mozilla Bug 436801</a>
+<p id="display"><iframe id="testFrame" src="bug436801-data.xml"></iframe></p>
+<div id="content" style="display: none">
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+
+addLoadEvent(function () {
+  var doc = SpecialPowers.wrap($("testFrame")).contentDocument;
+
+  checkNode(doc.getElementById("feedTitleText"), [
+    "ELEMENT", "h1", { "xml:base": "http://www.example.com/foo/bar/" }, [
+      ["TEXT", "Example of a "],
+      ["ELEMENT", "em", [
+        ["TEXT", "special"],
+      ]],
+      ["TEXT", " feed ("],
+      ["ELEMENT", "img", { "src": "baz.png" }],
+      ["TEXT", ")"],
+    ]
+  ]);
+
+  checkNode(doc.getElementById("feedSubtitleText"), [
+    "ELEMENT", "h2", { "xml:base": "http://www.example.com/foo/bar/" }, [
+      ["TEXT", "With a "],
+      ["ELEMENT", "em", [
+        ["TEXT", "special"],
+      ]],
+      ["TEXT", " subtitle ("],
+      ["ELEMENT", "img", { "src": "baz.png" }],
+      ["TEXT", ")"],
+    ]
+  ]);
+
+  checkNode(doc.querySelector(".entry").firstChild.firstChild.firstChild, [
+    "ELEMENT", "span", { "xml:base": "http://www.example.com/foo/bar/" }, [
+      ["TEXT", "Some "],
+      ["ELEMENT", "abbr", { title: "Extensible Hyper-text Mark-up Language" }, [
+        ["TEXT", "XHTML"],
+      ]],
+      ["TEXT", " examples ("],
+      ["ELEMENT", "img", { "src": "baz.png" }],
+      ["TEXT", ")"],
+    ]
+  ]);
+
+  checkNode(doc.querySelectorAll(".entry")[1].firstChild.firstChild.firstChild, [
+    "ELEMENT", "span", { "xml:base": "http://www.example.com/foo/bar/" }, [
+      ["TEXT", "Some "],
+      ["ELEMENT", "abbr", { title: "Hyper-text Mark-up Language" }, [
+        ["TEXT", "HTML"],
+      ]],
+      ["TEXT", " examples ("],
+      ["ELEMENT", "img", { "src": "baz.png" }],
+      ["TEXT", ")"],
+    ]
+  ]);
+});
+
+addLoadEvent(SimpleTest.finish);
+
+function checkNode(node, schema) {
+  var typeName = schema.shift() + "_NODE";
+  var type = Node[typeName];
+  is(node.nodeType, type, "Node should be expected type " + typeName);
+  if (type == Node.TEXT_NODE) {
+    var text = schema.shift();
+    is(node.data, text, "Text should match");
+    return;
+  }
+  // type == Node.ELEMENT_NODE
+  var tag = schema.shift();
+  is(node.localName, tag, "Element should have expected tag");
+  while (schema.length) {
+    let val = schema.shift();
+    if (Array.isArray(val))
+      var childSchema = val;
+    else
+      var attrSchema = val;
+  }
+  if (attrSchema) {
+    var nsTable = {
+      xml: "http://www.w3.org/XML/1998/namespace",
+    };
+    for (var name in attrSchema) {
+      var [ns, nsName] = name.split(":");
+      let val = nsName ? node.getAttributeNS(nsTable[ns], nsName) :
+                node.getAttribute(name);
+      is(val, attrSchema[name], "Attribute " + name + " should match");
+    }
+  }
+  if (childSchema) {
+    var numChildren = node.childNodes.length;
+    is(childSchema.length, numChildren,
+       "Element should have expected number of children");
+    for (var i = 0; i < numChildren; i++)
+      checkNode(node.childNodes[i], childSchema[i]);
+  }
+}
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/browser/components/feeds/test/test_bug494328.html b/browser/components/feeds/test/test_bug494328.html
new file mode 100644
index 000000000..054f62c1d
--- /dev/null
+++ b/browser/components/feeds/test/test_bug494328.html
@@ -0,0 +1,36 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=494328
+-->
+<head>
+  <title>Test for bug 494328</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=494328">Mozilla Bug 494328</a>
+<p id="display"><iframe id="testFrame" src="bug494328-data.xml"></iframe></p>
+<div id="content" style="display: none">
+  
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 494328 **/
+SimpleTest.waitForExplicitFinish();
+
+addLoadEvent(function() {
+  var links = SpecialPowers.wrap($("testFrame")).contentDocument.getElementById("feedContent").querySelectorAll("div.enclosure > a");
+  is(links[0].textContent, "Episode 1", "filename decoded incorrectly");
+  is(links[1].textContent, "Episode #2", "filename decoded incorrectly");
+  is(links[2].textContent, "http://www.example.com/podcasts/Episode #3/", "filename decoded incorrectly");
+  is(links[3].textContent, "Is This Episode #4?", "filename decoded incorrectly");
+});
+addLoadEvent(SimpleTest.finish);
+
+</script>
+</pre>
+</body>
+</html>
+
diff --git a/browser/components/feeds/test/test_bug589543.html b/browser/components/feeds/test/test_bug589543.html
new file mode 100644
index 000000000..cee2a9661
--- /dev/null
+++ b/browser/components/feeds/test/test_bug589543.html
@@ -0,0 +1,32 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=589543
+-->
+<head>
+  <title>Test feed preview subscribe UI</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=589543">Mozilla Bug 589543</a>
+<p id="display"><iframe id="testFrame" src="bug589543-data.xml"></iframe></p>
+<div id="content" style="display: none">
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 589543 **/
+SimpleTest.waitForExplicitFinish();
+
+addLoadEvent(function() {
+  var doc = SpecialPowers.wrap($("testFrame")).contentDocument;
+  var popup = doc.getElementById("handlersMenuList");
+  isnot(popup, null, "Feed preview should have a handlers popup");
+});
+addLoadEvent(SimpleTest.finish);
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/browser/components/feeds/test/test_registerHandler.html b/browser/components/feeds/test/test_registerHandler.html
new file mode 100644
index 000000000..34e61d034
--- /dev/null
+++ b/browser/components/feeds/test/test_registerHandler.html
@@ -0,0 +1,85 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=402788
+-->
+<head>
+  <title>Test for Bug 402788</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=402788">Mozilla Bug 402788</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+  
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 402788 **/
+
+  // return false if an exception has been catched, true otherwise
+  function testRegisterHandler(aIsProtocol, aTxt, aUri, aTitle)
+  {
+    try {
+      if (aIsProtocol)
+        navigator.registerProtocolHandler(aTxt, aUri, aTitle);
+      else
+        navigator.registerContentHandler(aTxt, aUri, aTitle);
+    }
+    catch (e) {
+      return false;
+    }
+
+    return true;
+  }
+
+  ok(navigator.registerProtocolHandler, "navigator.registerProtocolHandler should be defined");
+  ok(navigator.registerContentHandler, "navigator.registerContentHandler should be defined");
+
+  // testing a generic case
+  is(testRegisterHandler(true, "foo", "http://mochi.test:8888/%s", "Foo handler"), true, "registering a foo protocol handler should work");
+  is(testRegisterHandler(false, "application/rss+xml", "http://mochi.test:8888/%s", "Foo handler"), true, "registering a foo content handler should work");
+
+  // testing with wrong uris
+  is(testRegisterHandler(true, "foo", "http://mochi.test:8888/", "Foo handler"), false, "a protocol handler uri should contain %s");
+  is(testRegisterHandler(false, "application/rss+xml", "http://mochi.test:8888/", "Foo handler"), false, "a content handler uri should contain %s");
+
+  // the spec explicitly allows relative urls to be passed
+  is(testRegisterHandler(true, "foo", "foo/%s", "Foo handler"), true, "a protocol handler uri should be valid");
+  is(testRegisterHandler(false, "application/rss+xml", "foo/%s", "Foo handler"), true, "a content handler uri should be valid");
+
+  // we should only accept to register when the handler has the same host as the current page (bug 402287)
+  is(testRegisterHandler(true, "foo", "http://remotehost:8888/%s", "Foo handler"), false, "registering a foo protocol handler with a different host should not work");
+  is(testRegisterHandler(false, "application/rss+xml", "http://remotehost:8888/%s", "Foo handler"), false, "registering a foo content handler with a different host should not work");
+
+  // restriction to http(s) for the uri of the handler (bug 401343)
+  // https should work (http already tested in the generic case)
+  is(testRegisterHandler(true, "foo", "https://mochi.test:8888/%s", "Foo handler"), true, "registering a foo protocol handler with https scheme should work");
+  is(testRegisterHandler(false, "application/rss+xml", "https://mochi.test:8888/%s", "Foo handler"), true, "registering a foo content handler with https scheme should work");
+  // ftp should not work
+  is(testRegisterHandler(true, "foo", "ftp://mochi.test:8888/%s", "Foo handler"), false, "registering a foo protocol handler with ftp scheme should not work");
+  is(testRegisterHandler(false, "application/rss+xml", "ftp://mochi.test:8888/%s", "Foo handler"), false, "registering a foo content handler with ftp scheme should not work");
+  // chrome should not work
+  is(testRegisterHandler(true, "foo", "chrome://mochi.test:8888/%s", "Foo handler"), false, "registering a foo protocol handler with chrome scheme should not work");
+  is(testRegisterHandler(false, "application/rss+xml", "chrome://mochi.test:8888/%s", "Foo handler"), false, "registering a foo content handler with chrome scheme should not work");
+  // foo should not work
+  is(testRegisterHandler(true, "foo", "foo://mochi.test:8888/%s", "Foo handler"), false, "registering a foo protocol handler with foo scheme should not work");
+  is(testRegisterHandler(false, "application/rss+xml", "foo://mochi.test:8888/%s", "Foo handler"), false, "registering a foo content handler with foo scheme should not work");
+
+  // for security reasons, protocol handlers should never be registered for some schemes (chrome, vbscript, ...) (bug 402788)
+  is(testRegisterHandler(true, "chrome", "http://mochi.test:8888/%s", "chrome handler"), false, "registering a chrome protocol handler should not work");
+  is(testRegisterHandler(true, "vbscript", "http://mochi.test:8888/%s", "vbscript handler"), false, "registering a vbscript protocol handler should not work");
+  is(testRegisterHandler(true, "javascript", "http://mochi.test:8888/%s", "javascript handler"), false, "registering a javascript protocol handler should not work");
+  is(testRegisterHandler(true, "moz-icon", "http://mochi.test:8888/%s", "moz-icon handler"), false, "registering a moz-icon protocol handler should not work");
+
+  // for security reasons, content handlers should never be registered for some types (html, ...)
+  is(testRegisterHandler(false, "application/rss+xml", "http://mochi.test:8888/%s", "Foo handler"), true, "registering rss content handlers should work");
+  is(testRegisterHandler(false, "application/atom+xml", "http://mochi.test:8888/%s", "Foo handler"), true, "registering atom content handlers should work");
+  todo_is(testRegisterHandler(false, "text/html", "http://mochi.test:8888/%s", "Foo handler"), false, "registering html content handlers should not work"); // bug 403798
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/browser/components/feeds/test/unit/.eslintrc.js b/browser/components/feeds/test/unit/.eslintrc.js
new file mode 100644
index 000000000..d35787cd2
--- /dev/null
+++ b/browser/components/feeds/test/unit/.eslintrc.js
@@ -0,0 +1,7 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "../../../../../testing/xpcshell/xpcshell.eslintrc.js"
+  ]
+};
diff --git a/browser/components/feeds/test/unit/head_feeds.js b/browser/components/feeds/test/unit/head_feeds.js
new file mode 100644
index 000000000..3b1135ef7
--- /dev/null
+++ b/browser/components/feeds/test/unit/head_feeds.js
@@ -0,0 +1,5 @@
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cr = Components.results;
+
+var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
diff --git a/browser/components/feeds/test/unit/test_355473.js b/browser/components/feeds/test/unit/test_355473.js
new file mode 100644
index 000000000..8a20d1389
--- /dev/null
+++ b/browser/components/feeds/test/unit/test_355473.js
@@ -0,0 +1,43 @@
+var Cu = Components.utils;
+Cu.import("resource://gre/modules/NetUtil.jsm");
+
+function run_test() {
+  var feedFeedURI = ios.newURI("feed://example.com/feed.xml", null, null);
+  var httpFeedURI = ios.newURI("feed:http://example.com/feed.xml", null, null);
+  var httpURI = ios.newURI("http://example.com/feed.xml", null, null);
+
+  var httpsFeedURI =
+    ios.newURI("feed:https://example.com/feed.xml", null, null);
+  var httpsURI = ios.newURI("https://example.com/feed.xml", null, null);
+
+  var feedChannel = NetUtil.newChannel({
+    uri: feedFeedURI,
+    loadUsingSystemPrincipal: true
+  });
+
+  var httpChannel = NetUtil.newChannel({
+    uri: httpFeedURI,
+    loadUsingSystemPrincipal: true
+  });
+
+  var httpsChannel = NetUtil.newChannel({
+    uri: httpsFeedURI,
+    loadUsingSystemPrincipal: true
+  });
+
+  // not setting .originalURI to the original URI is naughty
+  do_check_true(feedFeedURI.equals(feedChannel.originalURI));
+  do_check_true(httpFeedURI.equals(httpChannel.originalURI));
+  do_check_true(httpsFeedURI.equals(httpsChannel.originalURI));
+
+  // actually using the horrible mess that's a feed: URI is suicidal
+  do_check_true(httpURI.equals(feedChannel.URI));
+  do_check_true(httpURI.equals(httpChannel.URI));
+  do_check_true(httpsURI.equals(httpsChannel.URI));
+
+  // check that we throw creating feed: URIs from file and ftp
+  Assert.throws(function() { ios.newURI("feed:ftp://example.com/feed.xml", null, null); },
+      "Should throw an exception when trying to create a feed: URI with an ftp: inner");
+  Assert.throws(function() { ios.newURI("feed:file:///var/feed.xml", null, null); },
+      "Should throw an exception when trying to create a feed: URI with a file: inner");
+}
diff --git a/browser/components/feeds/test/unit/test_758990.js b/browser/components/feeds/test/unit/test_758990.js
new file mode 100644
index 000000000..e6f88baf2
--- /dev/null
+++ b/browser/components/feeds/test/unit/test_758990.js
@@ -0,0 +1,42 @@
+function run_test() {
+  var success = false;
+  try {
+    ios.newURI("feed:javascript:alert('hi');", null, null);
+  }
+  catch (e) {
+    success = e.result == Cr.NS_ERROR_MALFORMED_URI;
+  }
+  if (!success)
+    do_throw("We didn't throw NS_ERROR_MALFORMED_URI creating a feed:javascript: URI");
+
+  success = false;
+  try {
+    ios.newURI("feed:data:text/html,hi", null, null);
+  }
+  catch (e) {
+    success = e.result == Cr.NS_ERROR_MALFORMED_URI;
+  }
+  if (!success)
+    do_throw("We didn't throw NS_ERROR_MALFORMED_URI creating a feed:data: URI");
+
+  success = false;
+  try {
+    ios.newURI("pcast:javascript:alert('hi');", null, null);
+  }
+  catch (e) {
+    success = e.result == Cr.NS_ERROR_MALFORMED_URI;
+  }
+  if (!success)
+    do_throw("We didn't throw NS_ERROR_MALFORMED_URI creating a pcast:javascript: URI");
+
+  success = false;
+  try {
+    ios.newURI("pcast:data:text/html,hi", null, null);
+  }
+  catch (e) {
+    success = e.result == Cr.NS_ERROR_MALFORMED_URI;
+  }
+  if (!success)
+    do_throw("We didn't throw NS_ERROR_MALFORMED_URI creating a pcast:data: URI");
+
+}
diff --git a/browser/components/feeds/test/unit/xpcshell.ini b/browser/components/feeds/test/unit/xpcshell.ini
new file mode 100644
index 000000000..9faf57396
--- /dev/null
+++ b/browser/components/feeds/test/unit/xpcshell.ini
@@ -0,0 +1,8 @@
+[DEFAULT]
+head = head_feeds.js
+tail = 
+firefox-appdir = browser
+skip-if = toolkit == 'android'
+
+[test_355473.js]
+[test_758990.js]
diff --git a/browser/components/feeds/test/valid-feed.xml b/browser/components/feeds/test/valid-feed.xml
new file mode 100644
index 000000000..0e700b6d8
--- /dev/null
+++ b/browser/components/feeds/test/valid-feed.xml
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+
+  <title>Example Feed</title>
+  <link href="http://example.org/"/>
+  <updated>2010-08-22T18:30:02Z</updated>
+
+  <author>
+    <name>John Doe</name>
+  </author>
+  <id>urn:uuid:e2df8375-99be-4848-b05e-b9d407555267</id>
+
+  <entry>
+
+    <title>Item</title>
+    <link href="http://example.org/first"/>
+    <id>urn:uuid:9e0f4bed-33d3-4a9d-97ab-ecaa31b3f14a</id>
+    <updated>2010-08-22T18:30:02Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>
diff --git a/browser/components/feeds/test/valid-unsniffable-feed.xml b/browser/components/feeds/test/valid-unsniffable-feed.xml
new file mode 100644
index 000000000..e75315739
--- /dev/null
+++ b/browser/components/feeds/test/valid-unsniffable-feed.xml
@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- 512 bytes!
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+  -->
+<feed xmlns="http://www.w3.org/2005/Atom">
+
+  <title>Example Feed</title>
+  <link href="http://example.org/"/>
+  <updated>2010-08-22T18:30:02Z</updated>
+
+  <author>
+    <name>John Doe</name>
+  </author>
+  <id>urn:uuid:e2df8375-99be-4848-b05e-b9d407555267</id>
+
+  <entry>
+
+    <title>Item</title>
+    <link href="http://example.org/first"/>
+    <id>urn:uuid:9e0f4bed-33d3-4a9d-97ab-ecaa31b3f14a</id>
+    <updated>2010-08-22T18:30:02Z</updated>
+
+    <summary>Some text.</summary>
+  </entry>
+
+</feed>