Add m-esr52 at 52.6.0

33 files changed, 7976 insertions, 0 deletions

diff --git a/browser/components/downloads/DownloadsCommon.jsm b/browser/components/downloads/DownloadsCommon.jsm
new file mode 100644
index 000000000..b6684817d
--- /dev/null
+++ b/browser/components/downloads/DownloadsCommon.jsm
@@ -0,0 +1,1553 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "DownloadsCommon",
+];
+
+/**
+ * Handles the Downloads panel shared methods and data access.
+ *
+ * This file includes the following constructors and global objects:
+ *
+ * DownloadsCommon
+ * This object is exposed directly to the consumers of this JavaScript module,
+ * and provides shared methods for all the instances of the user interface.
+ *
+ * DownloadsData
+ * Retrieves the list of past and completed downloads from the underlying
+ * Downloads API data, and provides asynchronous notifications allowing
+ * to build a consistent view of the available data.
+ *
+ * DownloadsIndicatorData
+ * This object registers itself with DownloadsData as a view, and transforms the
+ * notifications it receives into overall status data, that is then broadcast to
+ * the registered download status indicators.
+ */
+
+////////////////////////////////////////////////////////////////////////////////
+//// Globals
+
+const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+                                  "resource://gre/modules/NetUtil.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "PluralForm",
+                                  "resource://gre/modules/PluralForm.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
+                                  "resource://gre/modules/Downloads.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadUIHelper",
+                                  "resource://gre/modules/DownloadUIHelper.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadUtils",
+                                  "resource://gre/modules/DownloadUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+                                  "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm")
+XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
+                                  "resource://gre/modules/PlacesUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "PrivateBrowsingUtils",
+                                  "resource://gre/modules/PrivateBrowsingUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "RecentWindow",
+                                  "resource:///modules/RecentWindow.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+
+XPCOMUtils.defineLazyGetter(this, "DownloadsLogger", () => {
+  let { ConsoleAPI } = Cu.import("resource://gre/modules/Console.jsm", {});
+  let consoleOptions = {
+    maxLogLevelPref: "browser.download.loglevel",
+    prefix: "Downloads"
+  };
+  return new ConsoleAPI(consoleOptions);
+});
+
+const nsIDM = Ci.nsIDownloadManager;
+
+const kDownloadsStringBundleUrl =
+  "chrome://browser/locale/downloads/downloads.properties";
+
+const kDownloadsStringsRequiringFormatting = {
+  sizeWithUnits: true,
+  shortTimeLeftSeconds: true,
+  shortTimeLeftMinutes: true,
+  shortTimeLeftHours: true,
+  shortTimeLeftDays: true,
+  statusSeparator: true,
+  statusSeparatorBeforeNumber: true,
+  fileExecutableSecurityWarning: true
+};
+
+const kDownloadsStringsRequiringPluralForm = {
+  otherDownloads2: true
+};
+
+const kPartialDownloadSuffix = ".part";
+
+const kPrefBranch = Services.prefs.getBranch("browser.download.");
+
+var PrefObserver = {
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver,
+                                         Ci.nsISupportsWeakReference]),
+  getPref(name) {
+    try {
+      switch (typeof this.prefs[name]) {
+        case "boolean":
+          return kPrefBranch.getBoolPref(name);
+      }
+    } catch (ex) { }
+    return this.prefs[name];
+  },
+  observe(aSubject, aTopic, aData) {
+    if (this.prefs.hasOwnProperty(aData)) {
+      delete this[aData];
+      return this[aData] = this.getPref(aData);
+    }
+  },
+  register(prefs) {
+    this.prefs = prefs;
+    kPrefBranch.addObserver("", this, true);
+    for (let key in prefs) {
+      let name = key;
+      XPCOMUtils.defineLazyGetter(this, name, function () {
+        return PrefObserver.getPref(name);
+      });
+    }
+  },
+};
+
+PrefObserver.register({
+  // prefName: defaultValue
+  animateNotifications: true,
+  showPanelDropmarker: true,
+});
+
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsCommon
+
+/**
+ * This object is exposed directly to the consumers of this JavaScript module,
+ * and provides shared methods for all the instances of the user interface.
+ */
+this.DownloadsCommon = {
+  ATTENTION_NONE: "",
+  ATTENTION_SUCCESS: "success",
+  ATTENTION_WARNING: "warning",
+  ATTENTION_SEVERE: "severe",
+
+  /**
+   * Returns an object whose keys are the string names from the downloads string
+   * bundle, and whose values are either the translated strings or functions
+   * returning formatted strings.
+   */
+  get strings() {
+    let strings = {};
+    let sb = Services.strings.createBundle(kDownloadsStringBundleUrl);
+    let enumerator = sb.getSimpleEnumeration();
+    while (enumerator.hasMoreElements()) {
+      let string = enumerator.getNext().QueryInterface(Ci.nsIPropertyElement);
+      let stringName = string.key;
+      if (stringName in kDownloadsStringsRequiringFormatting) {
+        strings[stringName] = function () {
+          // Convert "arguments" to a real array before calling into XPCOM.
+          return sb.formatStringFromName(stringName,
+                                         Array.slice(arguments, 0),
+                                         arguments.length);
+        };
+      } else if (stringName in kDownloadsStringsRequiringPluralForm) {
+        strings[stringName] = function (aCount) {
+          // Convert "arguments" to a real array before calling into XPCOM.
+          let formattedString = sb.formatStringFromName(stringName,
+                                         Array.slice(arguments, 0),
+                                         arguments.length);
+          return PluralForm.get(aCount, formattedString);
+        };
+      } else {
+        strings[stringName] = string.value;
+      }
+    }
+    delete this.strings;
+    return this.strings = strings;
+  },
+
+  /**
+   * Generates a very short string representing the given time left.
+   *
+   * @param aSeconds
+   *        Value to be formatted.  It represents the number of seconds, it must
+   *        be positive but does not need to be an integer.
+   *
+   * @return Formatted string, for example "30s" or "2h".  The returned value is
+   *         maximum three characters long, at least in English.
+   */
+  formatTimeLeft(aSeconds) {
+    // Decide what text to show for the time
+    let seconds = Math.round(aSeconds);
+    if (!seconds) {
+      return "";
+    } else if (seconds <= 30) {
+      return DownloadsCommon.strings["shortTimeLeftSeconds"](seconds);
+    }
+    let minutes = Math.round(aSeconds / 60);
+    if (minutes < 60) {
+      return DownloadsCommon.strings["shortTimeLeftMinutes"](minutes);
+    }
+    let hours = Math.round(minutes / 60);
+    if (hours < 48) { // two days
+      return DownloadsCommon.strings["shortTimeLeftHours"](hours);
+    }
+    let days = Math.round(hours / 24);
+    return DownloadsCommon.strings["shortTimeLeftDays"](Math.min(days, 99));
+  },
+
+  /**
+   * Indicates whether we should show visual notification on the indicator
+   * when a download event is triggered.
+   */
+  get animateNotifications() {
+    return PrefObserver.animateNotifications;
+  },
+
+  /**
+   * Indicates whether we should show the dropmarker in the Downloads Panel.
+   */
+  get showPanelDropmarker() {
+    return PrefObserver.showPanelDropmarker;
+  },
+
+  /**
+   * Get access to one of the DownloadsData or PrivateDownloadsData objects,
+   * depending on the privacy status of the window in question.
+   *
+   * @param aWindow
+   *        The browser window which owns the download button.
+   */
+  getData(aWindow) {
+    if (PrivateBrowsingUtils.isContentWindowPrivate(aWindow)) {
+      return PrivateDownloadsData;
+    } else {
+      return DownloadsData;
+    }
+  },
+
+  /**
+   * Initializes the Downloads back-end and starts receiving events for both the
+   * private and non-private downloads data objects.
+   */
+  initializeAllDataLinks() {
+    DownloadsData.initializeDataLink();
+    PrivateDownloadsData.initializeDataLink();
+  },
+
+  /**
+   * Get access to one of the DownloadsIndicatorData or
+   * PrivateDownloadsIndicatorData objects, depending on the privacy status of
+   * the window in question.
+   */
+  getIndicatorData(aWindow) {
+    if (PrivateBrowsingUtils.isContentWindowPrivate(aWindow)) {
+      return PrivateDownloadsIndicatorData;
+    } else {
+      return DownloadsIndicatorData;
+    }
+  },
+
+  /**
+   * Returns a reference to the DownloadsSummaryData singleton - creating one
+   * in the process if one hasn't been instantiated yet.
+   *
+   * @param aWindow
+   *        The browser window which owns the download button.
+   * @param aNumToExclude
+   *        The number of items on the top of the downloads list to exclude
+   *        from the summary.
+   */
+  getSummary(aWindow, aNumToExclude) {
+    if (PrivateBrowsingUtils.isContentWindowPrivate(aWindow)) {
+      if (this._privateSummary) {
+        return this._privateSummary;
+      }
+      return this._privateSummary = new DownloadsSummaryData(true, aNumToExclude);
+    } else {
+      if (this._summary) {
+        return this._summary;
+      }
+      return this._summary = new DownloadsSummaryData(false, aNumToExclude);
+    }
+  },
+  _summary: null,
+  _privateSummary: null,
+
+  /**
+   * Returns the legacy state integer value for the provided Download object.
+   */
+  stateOfDownload(download) {
+    // Collapse state using the correct priority.
+    if (!download.stopped) {
+      return nsIDM.DOWNLOAD_DOWNLOADING;
+    }
+    if (download.succeeded) {
+      return nsIDM.DOWNLOAD_FINISHED;
+    }
+    if (download.error) {
+      if (download.error.becauseBlockedByParentalControls) {
+        return nsIDM.DOWNLOAD_BLOCKED_PARENTAL;
+      }
+      if (download.error.becauseBlockedByReputationCheck) {
+        return nsIDM.DOWNLOAD_DIRTY;
+      }
+      return nsIDM.DOWNLOAD_FAILED;
+    }
+    if (download.canceled) {
+      if (download.hasPartialData) {
+        return nsIDM.DOWNLOAD_PAUSED;
+      }
+      return nsIDM.DOWNLOAD_CANCELED;
+    }
+    return nsIDM.DOWNLOAD_NOTSTARTED;
+  },
+
+  /**
+   * Helper function required because the Downloads Panel and the Downloads View
+   * don't share the controller yet.
+   */
+  removeAndFinalizeDownload(download) {
+    Downloads.getList(Downloads.ALL)
+             .then(list => list.remove(download))
+             .then(() => download.finalize(true))
+             .catch(Cu.reportError);
+  },
+
+  /**
+   * Given an iterable collection of Download objects, generates and returns
+   * statistics about that collection.
+   *
+   * @param downloads An iterable collection of Download objects.
+   *
+   * @return Object whose properties are the generated statistics. Currently,
+   *         we return the following properties:
+   *
+   *         numActive       : The total number of downloads.
+   *         numPaused       : The total number of paused downloads.
+   *         numDownloading  : The total number of downloads being downloaded.
+   *         totalSize       : The total size of all downloads once completed.
+   *         totalTransferred: The total amount of transferred data for these
+   *                           downloads.
+   *         slowestSpeed    : The slowest download rate.
+   *         rawTimeLeft     : The estimated time left for the downloads to
+   *                           complete.
+   *         percentComplete : The percentage of bytes successfully downloaded.
+   */
+  summarizeDownloads(downloads) {
+    let summary = {
+      numActive: 0,
+      numPaused: 0,
+      numDownloading: 0,
+      totalSize: 0,
+      totalTransferred: 0,
+      // slowestSpeed is Infinity so that we can use Math.min to
+      // find the slowest speed. We'll set this to 0 afterwards if
+      // it's still at Infinity by the time we're done iterating all
+      // download.
+      slowestSpeed: Infinity,
+      rawTimeLeft: -1,
+      percentComplete: -1
+    }
+
+    for (let download of downloads) {
+      summary.numActive++;
+
+      if (!download.stopped) {
+        summary.numDownloading++;
+        if (download.hasProgress && download.speed > 0) {
+          let sizeLeft = download.totalBytes - download.currentBytes;
+          summary.rawTimeLeft = Math.max(summary.rawTimeLeft,
+                                         sizeLeft / download.speed);
+          summary.slowestSpeed = Math.min(summary.slowestSpeed,
+                                          download.speed);
+        }
+      } else if (download.canceled && download.hasPartialData) {
+        summary.numPaused++;
+      }
+
+      // Only add to total values if we actually know the download size.
+      if (download.succeeded) {
+        summary.totalSize += download.target.size;
+        summary.totalTransferred += download.target.size;
+      } else if (download.hasProgress) {
+        summary.totalSize += download.totalBytes;
+        summary.totalTransferred += download.currentBytes;
+      }
+    }
+
+    if (summary.totalSize != 0) {
+      summary.percentComplete = (summary.totalTransferred /
+                                 summary.totalSize) * 100;
+    }
+
+    if (summary.slowestSpeed == Infinity) {
+      summary.slowestSpeed = 0;
+    }
+
+    return summary;
+  },
+
+  /**
+   * If necessary, smooths the estimated number of seconds remaining for one
+   * or more downloads to complete.
+   *
+   * @param aSeconds
+   *        Current raw estimate on number of seconds left for one or more
+   *        downloads. This is a floating point value to help get sub-second
+   *        accuracy for current and future estimates.
+   */
+  smoothSeconds(aSeconds, aLastSeconds) {
+    // We apply an algorithm similar to the DownloadUtils.getTimeLeft function,
+    // though tailored to a single time estimation for all downloads.  We never
+    // apply something if the new value is less than half the previous value.
+    let shouldApplySmoothing = aLastSeconds >= 0 &&
+                               aSeconds > aLastSeconds / 2;
+    if (shouldApplySmoothing) {
+      // Apply hysteresis to favor downward over upward swings.  Trust only 30%
+      // of the new value if lower, and 10% if higher (exponential smoothing).
+      let diff = aSeconds - aLastSeconds;
+      aSeconds = aLastSeconds + (diff < 0 ? .3 : .1) * diff;
+
+      // If the new time is similar, reuse something close to the last time
+      // left, but subtract a little to provide forward progress.
+      diff = aSeconds - aLastSeconds;
+      let diffPercent = diff / aLastSeconds * 100;
+      if (Math.abs(diff) < 5 || Math.abs(diffPercent) < 5) {
+        aSeconds = aLastSeconds - (diff < 0 ? .4 : .2);
+      }
+    }
+
+    // In the last few seconds of downloading, we are always subtracting and
+    // never adding to the time left.  Ensure that we never fall below one
+    // second left until all downloads are actually finished.
+    return aLastSeconds = Math.max(aSeconds, 1);
+  },
+
+  /**
+   * Opens a downloaded file.
+   *
+   * @param aFile
+   *        the downloaded file to be opened.
+   * @param aMimeInfo
+   *        the mime type info object.  May be null.
+   * @param aOwnerWindow
+   *        the window with which this action is associated.
+   */
+  openDownloadedFile(aFile, aMimeInfo, aOwnerWindow) {
+    if (!(aFile instanceof Ci.nsIFile)) {
+      throw new Error("aFile must be a nsIFile object");
+    }
+    if (aMimeInfo && !(aMimeInfo instanceof Ci.nsIMIMEInfo)) {
+      throw new Error("Invalid value passed for aMimeInfo");
+    }
+    if (!(aOwnerWindow instanceof Ci.nsIDOMWindow)) {
+      throw new Error("aOwnerWindow must be a dom-window object");
+    }
+
+    let promiseShouldLaunch;
+    if (aFile.isExecutable()) {
+      // We get a prompter for the provided window here, even though anchoring
+      // to the most recently active window should work as well.
+      promiseShouldLaunch =
+        DownloadUIHelper.getPrompter(aOwnerWindow)
+                        .confirmLaunchExecutable(aFile.path);
+    } else {
+      promiseShouldLaunch = Promise.resolve(true);
+    }
+
+    promiseShouldLaunch.then(shouldLaunch => {
+      if (!shouldLaunch) {
+        return;
+      }
+
+      // Actually open the file.
+      try {
+        if (aMimeInfo && aMimeInfo.preferredAction == aMimeInfo.useHelperApp) {
+          aMimeInfo.launchWithFile(aFile);
+          return;
+        }
+      } catch (ex) { }
+
+      // If either we don't have the mime info, or the preferred action failed,
+      // attempt to launch the file directly.
+      try {
+        aFile.launch();
+      } catch (ex) {
+        // If launch fails, try sending it through the system's external "file:"
+        // URL handler.
+        Cc["@mozilla.org/uriloader/external-protocol-service;1"]
+          .getService(Ci.nsIExternalProtocolService)
+          .loadUrl(NetUtil.newURI(aFile));
+      }
+    }).then(null, Cu.reportError);
+  },
+
+  /**
+   * Show a downloaded file in the system file manager.
+   *
+   * @param aFile
+   *        a downloaded file.
+   */
+  showDownloadedFile(aFile) {
+    if (!(aFile instanceof Ci.nsIFile)) {
+      throw new Error("aFile must be a nsIFile object");
+    }
+    try {
+      // Show the directory containing the file and select the file.
+      aFile.reveal();
+    } catch (ex) {
+      // If reveal fails for some reason (e.g., it's not implemented on unix
+      // or the file doesn't exist), try using the parent if we have it.
+      let parent = aFile.parent;
+      if (parent) {
+        this.showDirectory(parent);
+      }
+    }
+  },
+
+  /**
+   * Show the specified folder in the system file manager.
+   *
+   * @param aDirectory
+   *        a directory to be opened with system file manager.
+   */
+  showDirectory(aDirectory) {
+    if (!(aDirectory instanceof Ci.nsIFile)) {
+      throw new Error("aDirectory must be a nsIFile object");
+    }
+    try {
+      aDirectory.launch();
+    } catch (ex) {
+      // If launch fails (probably because it's not implemented), let
+      // the OS handler try to open the directory.
+      Cc["@mozilla.org/uriloader/external-protocol-service;1"]
+        .getService(Ci.nsIExternalProtocolService)
+        .loadUrl(NetUtil.newURI(aDirectory));
+    }
+  },
+
+  /**
+   * Displays an alert message box which asks the user if they want to
+   * unblock the downloaded file or not.
+   *
+   * @param options
+   *        An object with the following properties:
+   *        {
+   *          verdict:
+   *            The detailed reason why the download was blocked, according to
+   *            the "Downloads.Error.BLOCK_VERDICT_" constants. If an unknown
+   *            reason is specified, "Downloads.Error.BLOCK_VERDICT_MALWARE" is
+   *            assumed.
+   *          window:
+   *            The window with which this action is associated.
+   *          dialogType:
+   *            String that determines which actions are available:
+   *             - "unblock" to offer just "unblock".
+   *             - "chooseUnblock" to offer "unblock" and "confirmBlock".
+   *             - "chooseOpen" to offer "open" and "confirmBlock".
+   *        }
+   *
+   * @return {Promise}
+   * @resolves String representing the action that should be executed:
+   *            - "open" to allow the download and open the file.
+   *            - "unblock" to allow the download without opening the file.
+   *            - "confirmBlock" to delete the blocked data permanently.
+   *            - "cancel" to do nothing and cancel the operation.
+   */
+  confirmUnblockDownload: Task.async(function* ({ verdict, window,
+                                                  dialogType }) {
+    let s = DownloadsCommon.strings;
+
+    // All the dialogs have an action button and a cancel button, while only
+    // some of them have an additonal button to remove the file. The cancel
+    // button must always be the one at BUTTON_POS_1 because this is the value
+    // returned by confirmEx when using ESC or closing the dialog (bug 345067).
+    let title = s.unblockHeaderUnblock;
+    let firstButtonText = s.unblockButtonUnblock;
+    let firstButtonAction = "unblock";
+    let buttonFlags =
+        (Ci.nsIPrompt.BUTTON_TITLE_IS_STRING * Ci.nsIPrompt.BUTTON_POS_0) +
+        (Ci.nsIPrompt.BUTTON_TITLE_CANCEL * Ci.nsIPrompt.BUTTON_POS_1);
+
+    switch (dialogType) {
+      case "unblock":
+        // Use only the unblock action. The default is to cancel.
+        buttonFlags += Ci.nsIPrompt.BUTTON_POS_1_DEFAULT;
+        break;
+      case "chooseUnblock":
+        // Use the unblock and remove file actions. The default is remove file.
+        buttonFlags +=
+          (Ci.nsIPrompt.BUTTON_TITLE_IS_STRING * Ci.nsIPrompt.BUTTON_POS_2) +
+          Ci.nsIPrompt.BUTTON_POS_2_DEFAULT;
+        break;
+      case "chooseOpen":
+        // Use the unblock and open file actions. The default is open file.
+        title = s.unblockHeaderOpen;
+        firstButtonText = s.unblockButtonOpen;
+        firstButtonAction = "open";
+        buttonFlags +=
+          (Ci.nsIPrompt.BUTTON_TITLE_IS_STRING * Ci.nsIPrompt.BUTTON_POS_2) +
+          Ci.nsIPrompt.BUTTON_POS_0_DEFAULT;
+        break;
+      default:
+        Cu.reportError("Unexpected dialog type: " + dialogType);
+        return "cancel";
+    }
+
+    let message;
+    switch (verdict) {
+      case Downloads.Error.BLOCK_VERDICT_UNCOMMON:
+        message = s.unblockTypeUncommon2;
+        break;
+      case Downloads.Error.BLOCK_VERDICT_POTENTIALLY_UNWANTED:
+        message = s.unblockTypePotentiallyUnwanted2;
+        break;
+      default: // Assume Downloads.Error.BLOCK_VERDICT_MALWARE
+        message = s.unblockTypeMalware;
+        break;
+    }
+    message += "\n\n" + s.unblockTip2;
+
+    Services.ww.registerNotification(function onOpen(subj, topic) {
+      if (topic == "domwindowopened" && subj instanceof Ci.nsIDOMWindow) {
+        // Make sure to listen for "DOMContentLoaded" because it is fired
+        // before the "load" event.
+        subj.addEventListener("DOMContentLoaded", function onLoad() {
+          subj.removeEventListener("DOMContentLoaded", onLoad);
+          if (subj.document.documentURI ==
+              "chrome://global/content/commonDialog.xul") {
+            Services.ww.unregisterNotification(onOpen);
+            let dialog = subj.document.getElementById("commonDialog");
+            if (dialog) {
+              // Change the dialog to use a warning icon.
+              dialog.classList.add("alert-dialog");
+            }
+          }
+        });
+      }
+    });
+
+    let rv = Services.prompt.confirmEx(window, title, message, buttonFlags,
+                                       firstButtonText, null,
+                                       s.unblockButtonConfirmBlock, null, {});
+    return [firstButtonAction, "cancel", "confirmBlock"][rv];
+  }),
+};
+
+XPCOMUtils.defineLazyGetter(this.DownloadsCommon, "log", () => {
+  return DownloadsLogger.log.bind(DownloadsLogger);
+});
+XPCOMUtils.defineLazyGetter(this.DownloadsCommon, "error", () => {
+  return DownloadsLogger.error.bind(DownloadsLogger);
+});
+
+/**
+ * Returns true if we are executing on Windows Vista or a later version.
+ */
+XPCOMUtils.defineLazyGetter(DownloadsCommon, "isWinVistaOrHigher", function () {
+  let os = Cc["@mozilla.org/xre/app-info;1"].getService(Ci.nsIXULRuntime).OS;
+  if (os != "WINNT") {
+    return false;
+  }
+  let sysInfo = Cc["@mozilla.org/system-info;1"].getService(Ci.nsIPropertyBag2);
+  return parseFloat(sysInfo.getProperty("version")) >= 6;
+});
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsData
+
+/**
+ * Retrieves the list of past and completed downloads from the underlying
+ * Download Manager data, and provides asynchronous notifications allowing to
+ * build a consistent view of the available data.
+ *
+ * This object responds to real-time changes in the underlying Download Manager
+ * data.  For example, the deletion of one or more downloads is notified through
+ * the nsIObserver interface, while any state or progress change is notified
+ * through the nsIDownloadProgressListener interface.
+ *
+ * Note that using this object does not automatically start the Download Manager
+ * service.  Consumers will see an empty list of downloads until the service is
+ * actually started.  This is useful to display a neutral progress indicator in
+ * the main browser window until the autostart timeout elapses.
+ *
+ * Note that DownloadsData and PrivateDownloadsData are two equivalent singleton
+ * objects, one accessing non-private downloads, and the other accessing private
+ * ones.
+ */
+function DownloadsDataCtor(aPrivate) {
+  this._isPrivate = aPrivate;
+
+  // Contains all the available Download objects and their integer state.
+  this.oldDownloadStates = new Map();
+
+  // Array of view objects that should be notified when the available download
+  // data changes.
+  this._views = [];
+}
+
+DownloadsDataCtor.prototype = {
+  /**
+   * Starts receiving events for current downloads.
+   */
+  initializeDataLink() {
+    if (!this._dataLinkInitialized) {
+      let promiseList = Downloads.getList(this._isPrivate ? Downloads.PRIVATE
+                                                          : Downloads.PUBLIC);
+      promiseList.then(list => list.addView(this)).then(null, Cu.reportError);
+      this._dataLinkInitialized = true;
+    }
+  },
+  _dataLinkInitialized: false,
+
+  /**
+   * Iterator for all the available Download objects. This is empty until the
+   * data has been loaded using the JavaScript API for downloads.
+   */
+  get downloads() {
+    return this.oldDownloadStates.keys();
+  },
+
+  /**
+   * True if there are finished downloads that can be removed from the list.
+   */
+  get canRemoveFinished() {
+    for (let download of this.downloads) {
+      // Stopped, paused, and failed downloads with partial data are removed.
+      if (download.stopped && !(download.canceled && download.hasPartialData)) {
+        return true;
+      }
+    }
+    return false;
+  },
+
+  /**
+   * Asks the back-end to remove finished downloads from the list.
+   */
+  removeFinished() {
+    let promiseList = Downloads.getList(this._isPrivate ? Downloads.PRIVATE
+                                                        : Downloads.PUBLIC);
+    promiseList.then(list => list.removeFinished())
+               .then(null, Cu.reportError);
+    let indicatorData = this._isPrivate ? PrivateDownloadsIndicatorData
+                                        : DownloadsIndicatorData;
+    indicatorData.attention = DownloadsCommon.ATTENTION_NONE;
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Integration with the asynchronous Downloads back-end
+
+  onDownloadAdded(download) {
+    // Download objects do not store the end time of downloads, as the Downloads
+    // API does not need to persist this information for all platforms. Once a
+    // download terminates on a Desktop browser, it becomes a history download,
+    // for which the end time is stored differently, as a Places annotation.
+    download.endTime = Date.now();
+
+    this.oldDownloadStates.set(download,
+                               DownloadsCommon.stateOfDownload(download));
+
+    for (let view of this._views) {
+      view.onDownloadAdded(download, true);
+    }
+  },
+
+  onDownloadChanged(download) {
+    let oldState = this.oldDownloadStates.get(download);
+    let newState = DownloadsCommon.stateOfDownload(download);
+    this.oldDownloadStates.set(download, newState);
+
+    if (oldState != newState) {
+      if (download.succeeded ||
+          (download.canceled && !download.hasPartialData) ||
+          download.error) {
+        // Store the end time that may be displayed by the views.
+        download.endTime = Date.now();
+
+        // This state transition code should actually be located in a Downloads
+        // API module (bug 941009).  Moreover, the fact that state is stored as
+        // annotations should be ideally hidden behind methods of
+        // nsIDownloadHistory (bug 830415).
+        if (!this._isPrivate) {
+          try {
+            let downloadMetaData = {
+              state: DownloadsCommon.stateOfDownload(download),
+              endTime: download.endTime,
+            };
+            if (download.succeeded) {
+              downloadMetaData.fileSize = download.target.size;
+            }
+            if (download.error && download.error.reputationCheckVerdict) {
+              downloadMetaData.reputationCheckVerdict =
+                download.error.reputationCheckVerdict;
+            }
+
+            PlacesUtils.annotations.setPageAnnotation(
+                          NetUtil.newURI(download.source.url),
+                          "downloads/metaData",
+                          JSON.stringify(downloadMetaData), 0,
+                          PlacesUtils.annotations.EXPIRE_WITH_HISTORY);
+          } catch (ex) {
+            Cu.reportError(ex);
+          }
+        }
+      }
+
+      for (let view of this._views) {
+        try {
+          view.onDownloadStateChanged(download);
+        } catch (ex) {
+          Cu.reportError(ex);
+        }
+      }
+
+      if (download.succeeded ||
+          (download.error && download.error.becauseBlocked)) {
+        this._notifyDownloadEvent("finish");
+      }
+    }
+
+    if (!download.newDownloadNotified) {
+      download.newDownloadNotified = true;
+      this._notifyDownloadEvent("start");
+    }
+
+    for (let view of this._views) {
+      view.onDownloadChanged(download);
+    }
+  },
+
+  onDownloadRemoved(download) {
+    this.oldDownloadStates.delete(download);
+
+    for (let view of this._views) {
+      view.onDownloadRemoved(download);
+    }
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Registration of views
+
+  /**
+   * Adds an object to be notified when the available download data changes.
+   * The specified object is initialized with the currently available downloads.
+   *
+   * @param aView
+   *        DownloadsView object to be added.  This reference must be passed to
+   *        removeView before termination.
+   */
+  addView(aView) {
+    this._views.push(aView);
+    this._updateView(aView);
+  },
+
+  /**
+   * Removes an object previously added using addView.
+   *
+   * @param aView
+   *        DownloadsView object to be removed.
+   */
+  removeView(aView) {
+    let index = this._views.indexOf(aView);
+    if (index != -1) {
+      this._views.splice(index, 1);
+    }
+  },
+
+  /**
+   * Ensures that the currently loaded data is added to the specified view.
+   *
+   * @param aView
+   *        DownloadsView object to be initialized.
+   */
+  _updateView(aView) {
+    // Indicate to the view that a batch loading operation is in progress.
+    aView.onDataLoadStarting();
+
+    // Sort backwards by start time, ensuring that the most recent
+    // downloads are added first regardless of their state.
+    let downloadsArray = [...this.downloads];
+    downloadsArray.sort((a, b) => b.startTime - a.startTime);
+    downloadsArray.forEach(download => aView.onDownloadAdded(download, false));
+
+    // Notify the view that all data is available.
+    aView.onDataLoadCompleted();
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Notifications sent to the most recent browser window only
+
+  /**
+   * Set to true after the first download causes the downloads panel to be
+   * displayed.
+   */
+  get panelHasShownBefore() {
+    try {
+      return Services.prefs.getBoolPref("browser.download.panel.shown");
+    } catch (ex) { }
+    return false;
+  },
+
+  set panelHasShownBefore(aValue) {
+    Services.prefs.setBoolPref("browser.download.panel.shown", aValue);
+    return aValue;
+  },
+
+  /**
+   * Displays a new or finished download notification in the most recent browser
+   * window, if one is currently available with the required privacy type.
+   *
+   * @param aType
+   *        Set to "start" for new downloads, "finish" for completed downloads.
+   */
+  _notifyDownloadEvent(aType) {
+    DownloadsCommon.log("Attempting to notify that a new download has started or finished.");
+
+    // Show the panel in the most recent browser window, if present.
+    let browserWin = RecentWindow.getMostRecentBrowserWindow({ private: this._isPrivate });
+    if (!browserWin) {
+      return;
+    }
+
+    if (this.panelHasShownBefore) {
+      // For new downloads after the first one, don't show the panel
+      // automatically, but provide a visible notification in the topmost
+      // browser window, if the status indicator is already visible.
+      DownloadsCommon.log("Showing new download notification.");
+      browserWin.DownloadsIndicatorView.showEventNotification(aType);
+      return;
+    }
+    this.panelHasShownBefore = true;
+    browserWin.DownloadsPanel.showPanel();
+  }
+};
+
+XPCOMUtils.defineLazyGetter(this, "PrivateDownloadsData", function() {
+  return new DownloadsDataCtor(true);
+});
+
+XPCOMUtils.defineLazyGetter(this, "DownloadsData", function() {
+  return new DownloadsDataCtor(false);
+});
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsViewPrototype
+
+/**
+ * A prototype for an object that registers itself with DownloadsData as soon
+ * as a view is registered with it.
+ */
+const DownloadsViewPrototype = {
+  //////////////////////////////////////////////////////////////////////////////
+  //// Registration of views
+
+  /**
+   * Array of view objects that should be notified when the available status
+   * data changes.
+   *
+   * SUBCLASSES MUST OVERRIDE THIS PROPERTY.
+   */
+  _views: null,
+
+  /**
+   * Determines whether this view object is over the private or non-private
+   * downloads.
+   *
+   * SUBCLASSES MUST OVERRIDE THIS PROPERTY.
+   */
+  _isPrivate: false,
+
+  /**
+   * Adds an object to be notified when the available status data changes.
+   * The specified object is initialized with the currently available status.
+   *
+   * @param aView
+   *        View object to be added.  This reference must be
+   *        passed to removeView before termination.
+   */
+  addView(aView) {
+    // Start receiving events when the first of our views is registered.
+    if (this._views.length == 0) {
+      if (this._isPrivate) {
+        PrivateDownloadsData.addView(this);
+      } else {
+        DownloadsData.addView(this);
+      }
+    }
+
+    this._views.push(aView);
+    this.refreshView(aView);
+  },
+
+  /**
+   * Updates the properties of an object previously added using addView.
+   *
+   * @param aView
+   *        View object to be updated.
+   */
+  refreshView(aView) {
+    // Update immediately even if we are still loading data asynchronously.
+    // Subclasses must provide these two functions!
+    this._refreshProperties();
+    this._updateView(aView);
+  },
+
+  /**
+   * Removes an object previously added using addView.
+   *
+   * @param aView
+   *        View object to be removed.
+   */
+  removeView(aView) {
+    let index = this._views.indexOf(aView);
+    if (index != -1) {
+      this._views.splice(index, 1);
+    }
+
+    // Stop receiving events when the last of our views is unregistered.
+    if (this._views.length == 0) {
+      if (this._isPrivate) {
+        PrivateDownloadsData.removeView(this);
+      } else {
+        DownloadsData.removeView(this);
+      }
+    }
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Callback functions from DownloadsData
+
+  /**
+   * Indicates whether we are still loading downloads data asynchronously.
+   */
+  _loading: false,
+
+  /**
+   * Called before multiple downloads are about to be loaded.
+   */
+  onDataLoadStarting() {
+    this._loading = true;
+  },
+
+  /**
+   * Called after data loading finished.
+   */
+  onDataLoadCompleted() {
+    this._loading = false;
+  },
+
+  /**
+   * Called when a new download data item is available, either during the
+   * asynchronous data load or when a new download is started.
+   *
+   * @param download
+   *        Download object that was just added.
+   * @param newest
+   *        When true, indicates that this item is the most recent and should be
+   *        added in the topmost position.  This happens when a new download is
+   *        started.  When false, indicates that the item is the least recent
+   *        with regard to the items that have been already added. The latter
+   *        generally happens during the asynchronous data load.
+   *
+   * @note Subclasses should override this.
+   */
+  onDownloadAdded(download, newest) {
+    throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  /**
+   * Called when the overall state of a Download has changed. In particular,
+   * this is called only once when the download succeeds or is blocked
+   * permanently, and is never called if only the current progress changed.
+   *
+   * The onDownloadChanged notification will always be sent afterwards.
+   *
+   * @note Subclasses should override this.
+   */
+  onDownloadStateChanged(download) {
+    throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  /**
+   * Called every time any state property of a Download may have changed,
+   * including progress properties.
+   *
+   * Note that progress notification changes are throttled at the Downloads.jsm
+   * API level, and there is no throttling mechanism in the front-end.
+   *
+   * @note Subclasses should override this.
+   */
+  onDownloadChanged(download) {
+    throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  /**
+   * Called when a data item is removed, ensures that the widget associated with
+   * the view item is removed from the user interface.
+   *
+   * @param download
+   *        Download object that is being removed.
+   *
+   * @note Subclasses should override this.
+   */
+  onDownloadRemoved(download) {
+    throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  /**
+   * Private function used to refresh the internal properties being sent to
+   * each registered view.
+   *
+   * @note Subclasses should override this.
+   */
+  _refreshProperties() {
+    throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  /**
+   * Private function used to refresh an individual view.
+   *
+   * @note Subclasses should override this.
+   */
+  _updateView() {
+    throw Components.results.NS_ERROR_NOT_IMPLEMENTED;
+  },
+};
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsIndicatorData
+
+/**
+ * This object registers itself with DownloadsData as a view, and transforms the
+ * notifications it receives into overall status data, that is then broadcast to
+ * the registered download status indicators.
+ *
+ * Note that using this object does not automatically start the Download Manager
+ * service.  Consumers will see an empty list of downloads until the service is
+ * actually started.  This is useful to display a neutral progress indicator in
+ * the main browser window until the autostart timeout elapses.
+ */
+function DownloadsIndicatorDataCtor(aPrivate) {
+  this._isPrivate = aPrivate;
+  this._views = [];
+}
+DownloadsIndicatorDataCtor.prototype = {
+  __proto__: DownloadsViewPrototype,
+
+  /**
+   * Removes an object previously added using addView.
+   *
+   * @param aView
+   *        DownloadsIndicatorView object to be removed.
+   */
+  removeView(aView) {
+    DownloadsViewPrototype.removeView.call(this, aView);
+
+    if (this._views.length == 0) {
+      this._itemCount = 0;
+    }
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Callback functions from DownloadsData
+
+  onDataLoadCompleted() {
+    DownloadsViewPrototype.onDataLoadCompleted.call(this);
+    this._updateViews();
+  },
+
+  onDownloadAdded(download, newest) {
+    this._itemCount++;
+    this._updateViews();
+  },
+
+  onDownloadStateChanged(download) {
+    if (!download.succeeded && download.error && download.error.reputationCheckVerdict) {
+      switch (download.error.reputationCheckVerdict) {
+        case Downloads.Error.BLOCK_VERDICT_UNCOMMON: // fall-through
+        case Downloads.Error.BLOCK_VERDICT_POTENTIALLY_UNWANTED:
+          // Existing higher level attention indication trumps ATTENTION_WARNING.
+          if (this._attention != DownloadsCommon.ATTENTION_SEVERE) {
+            this.attention = DownloadsCommon.ATTENTION_WARNING;
+          }
+          break;
+        case Downloads.Error.BLOCK_VERDICT_MALWARE:
+          this.attention = DownloadsCommon.ATTENTION_SEVERE;
+          break;
+        default:
+          this.attention = DownloadsCommon.ATTENTION_SEVERE;
+          Cu.reportError("Unknown reputation verdict: " +
+                         download.error.reputationCheckVerdict);
+      }
+    } else if (download.succeeded) {
+      // Existing higher level attention indication trumps ATTENTION_SUCCESS.
+      if (this._attention != DownloadsCommon.ATTENTION_SEVERE &&
+          this._attention != DownloadsCommon.ATTENTION_WARNING) {
+        this.attention = DownloadsCommon.ATTENTION_SUCCESS;
+      }
+    } else if (download.error) {
+      // Existing higher level attention indication trumps ATTENTION_WARNING.
+      if (this._attention != DownloadsCommon.ATTENTION_SEVERE) {
+        this.attention = DownloadsCommon.ATTENTION_WARNING;
+      }
+    }
+
+    // Since the state of a download changed, reset the estimated time left.
+    this._lastRawTimeLeft = -1;
+    this._lastTimeLeft = -1;
+  },
+
+  onDownloadChanged(download) {
+    this._updateViews();
+  },
+
+  onDownloadRemoved(download) {
+    this._itemCount--;
+    this._updateViews();
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Propagation of properties to our views
+
+  // The following properties are updated by _refreshProperties and are then
+  // propagated to the views.  See _refreshProperties for details.
+  _hasDownloads: false,
+  _counter: "",
+  _percentComplete: -1,
+  _paused: false,
+
+  /**
+   * Indicates whether the download indicators should be highlighted.
+   */
+  set attention(aValue) {
+    this._attention = aValue;
+    this._updateViews();
+    return aValue;
+  },
+  _attention: DownloadsCommon.ATTENTION_NONE,
+
+  /**
+   * Indicates whether the user is interacting with downloads, thus the
+   * attention indication should not be shown even if requested.
+   */
+  set attentionSuppressed(aValue) {
+    this._attentionSuppressed = aValue;
+    this._attention = DownloadsCommon.ATTENTION_NONE;
+    this._updateViews();
+    return aValue;
+  },
+  _attentionSuppressed: false,
+
+  /**
+   * Computes aggregate values and propagates the changes to our views.
+   */
+  _updateViews() {
+    // Do not update the status indicators during batch loads of download items.
+    if (this._loading) {
+      return;
+    }
+
+    this._refreshProperties();
+    this._views.forEach(this._updateView, this);
+  },
+
+  /**
+   * Updates the specified view with the current aggregate values.
+   *
+   * @param aView
+   *        DownloadsIndicatorView object to be updated.
+   */
+  _updateView(aView) {
+    aView.hasDownloads = this._hasDownloads;
+    aView.counter = this._counter;
+    aView.percentComplete = this._percentComplete;
+    aView.paused = this._paused;
+    aView.attention = this._attentionSuppressed ? DownloadsCommon.ATTENTION_NONE
+                                                : this._attention;
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Property updating based on current download status
+
+  /**
+   * Number of download items that are available to be displayed.
+   */
+  _itemCount: 0,
+
+  /**
+   * Floating point value indicating the last number of seconds estimated until
+   * the longest download will finish.  We need to store this value so that we
+   * don't continuously apply smoothing if the actual download state has not
+   * changed.  This is set to -1 if the previous value is unknown.
+   */
+  _lastRawTimeLeft: -1,
+
+  /**
+   * Last number of seconds estimated until all in-progress downloads with a
+   * known size and speed will finish.  This value is stored to allow smoothing
+   * in case of small variations.  This is set to -1 if the previous value is
+   * unknown.
+   */
+  _lastTimeLeft: -1,
+
+  /**
+   * A generator function for the Download objects this summary is currently
+   * interested in. This generator is passed off to summarizeDownloads in order
+   * to generate statistics about the downloads we care about - in this case,
+   * it's all active downloads.
+   */
+  * _activeDownloads() {
+    let downloads = this._isPrivate ? PrivateDownloadsData.downloads
+                                    : DownloadsData.downloads;
+    for (let download of downloads) {
+      if (!download.stopped || (download.canceled && download.hasPartialData)) {
+        yield download;
+      }
+    }
+  },
+
+  /**
+   * Computes aggregate values based on the current state of downloads.
+   */
+  _refreshProperties() {
+    let summary =
+      DownloadsCommon.summarizeDownloads(this._activeDownloads());
+
+    // Determine if the indicator should be shown or get attention.
+    this._hasDownloads = (this._itemCount > 0);
+
+    // If all downloads are paused, show the progress indicator as paused.
+    this._paused = summary.numActive > 0 &&
+                   summary.numActive == summary.numPaused;
+
+    this._percentComplete = summary.percentComplete;
+
+    // Display the estimated time left, if present.
+    if (summary.rawTimeLeft == -1) {
+      // There are no downloads with a known time left.
+      this._lastRawTimeLeft = -1;
+      this._lastTimeLeft = -1;
+      this._counter = "";
+    } else {
+      // Compute the new time left only if state actually changed.
+      if (this._lastRawTimeLeft != summary.rawTimeLeft) {
+        this._lastRawTimeLeft = summary.rawTimeLeft;
+        this._lastTimeLeft = DownloadsCommon.smoothSeconds(summary.rawTimeLeft,
+                                                           this._lastTimeLeft);
+      }
+      this._counter = DownloadsCommon.formatTimeLeft(this._lastTimeLeft);
+    }
+  }
+};
+
+XPCOMUtils.defineLazyGetter(this, "PrivateDownloadsIndicatorData", function() {
+  return new DownloadsIndicatorDataCtor(true);
+});
+
+XPCOMUtils.defineLazyGetter(this, "DownloadsIndicatorData", function() {
+  return new DownloadsIndicatorDataCtor(false);
+});
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsSummaryData
+
+/**
+ * DownloadsSummaryData is a view for DownloadsData that produces a summary
+ * of all downloads after a certain exclusion point aNumToExclude. For example,
+ * if there were 5 downloads in progress, and a DownloadsSummaryData was
+ * constructed with aNumToExclude equal to 3, then that DownloadsSummaryData
+ * would produce a summary of the last 2 downloads.
+ *
+ * @param aIsPrivate
+ *        True if the browser window which owns the download button is a private
+ *        window.
+ * @param aNumToExclude
+ *        The number of items to exclude from the summary, starting from the
+ *        top of the list.
+ */
+function DownloadsSummaryData(aIsPrivate, aNumToExclude) {
+  this._numToExclude = aNumToExclude;
+  // Since we can have multiple instances of DownloadsSummaryData, we
+  // override these values from the prototype so that each instance can be
+  // completely separated from one another.
+  this._loading = false;
+
+  this._downloads = [];
+
+  // Floating point value indicating the last number of seconds estimated until
+  // the longest download will finish.  We need to store this value so that we
+  // don't continuously apply smoothing if the actual download state has not
+  // changed.  This is set to -1 if the previous value is unknown.
+  this._lastRawTimeLeft = -1;
+
+  // Last number of seconds estimated until all in-progress downloads with a
+  // known size and speed will finish.  This value is stored to allow smoothing
+  // in case of small variations.  This is set to -1 if the previous value is
+  // unknown.
+  this._lastTimeLeft = -1;
+
+  // The following properties are updated by _refreshProperties and are then
+  // propagated to the views.
+  this._showingProgress = false;
+  this._details = "";
+  this._description = "";
+  this._numActive = 0;
+  this._percentComplete = -1;
+
+  this._isPrivate = aIsPrivate;
+  this._views = [];
+}
+
+DownloadsSummaryData.prototype = {
+  __proto__: DownloadsViewPrototype,
+
+  /**
+   * Removes an object previously added using addView.
+   *
+   * @param aView
+   *        DownloadsSummary view to be removed.
+   */
+  removeView(aView) {
+    DownloadsViewPrototype.removeView.call(this, aView);
+
+    if (this._views.length == 0) {
+      // Clear out our collection of Download objects. If we ever have
+      // another view registered with us, this will get re-populated.
+      this._downloads = [];
+    }
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Callback functions from DownloadsData - see the documentation in
+  //// DownloadsViewPrototype for more information on what these functions
+  //// are used for.
+
+  onDataLoadCompleted() {
+    DownloadsViewPrototype.onDataLoadCompleted.call(this);
+    this._updateViews();
+  },
+
+  onDownloadAdded(download, newest) {
+    if (newest) {
+      this._downloads.unshift(download);
+    } else {
+      this._downloads.push(download);
+    }
+
+    this._updateViews();
+  },
+
+  onDownloadStateChanged() {
+    // Since the state of a download changed, reset the estimated time left.
+    this._lastRawTimeLeft = -1;
+    this._lastTimeLeft = -1;
+  },
+
+  onDownloadChanged() {
+    this._updateViews();
+  },
+
+  onDownloadRemoved(download) {
+    let itemIndex = this._downloads.indexOf(download);
+    this._downloads.splice(itemIndex, 1);
+    this._updateViews();
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Propagation of properties to our views
+
+  /**
+   * Computes aggregate values and propagates the changes to our views.
+   */
+  _updateViews() {
+    // Do not update the status indicators during batch loads of download items.
+    if (this._loading) {
+      return;
+    }
+
+    this._refreshProperties();
+    this._views.forEach(this._updateView, this);
+  },
+
+  /**
+   * Updates the specified view with the current aggregate values.
+   *
+   * @param aView
+   *        DownloadsIndicatorView object to be updated.
+   */
+  _updateView(aView) {
+    aView.showingProgress = this._showingProgress;
+    aView.percentComplete = this._percentComplete;
+    aView.description = this._description;
+    aView.details = this._details;
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Property updating based on current download status
+
+  /**
+   * A generator function for the Download objects this summary is currently
+   * interested in. This generator is passed off to summarizeDownloads in order
+   * to generate statistics about the downloads we care about - in this case,
+   * it's the downloads in this._downloads after the first few to exclude,
+   * which was set when constructing this DownloadsSummaryData instance.
+   */
+  * _downloadsForSummary() {
+    if (this._downloads.length > 0) {
+      for (let i = this._numToExclude; i < this._downloads.length; ++i) {
+        yield this._downloads[i];
+      }
+    }
+  },
+
+  /**
+   * Computes aggregate values based on the current state of downloads.
+   */
+  _refreshProperties() {
+    // Pre-load summary with default values.
+    let summary =
+      DownloadsCommon.summarizeDownloads(this._downloadsForSummary());
+
+    this._description = DownloadsCommon.strings
+                                       .otherDownloads2(summary.numActive);
+    this._percentComplete = summary.percentComplete;
+
+    // If all downloads are paused, show the progress indicator as paused.
+    this._showingProgress = summary.numDownloading > 0 ||
+                            summary.numPaused > 0;
+
+    // Display the estimated time left, if present.
+    if (summary.rawTimeLeft == -1) {
+      // There are no downloads with a known time left.
+      this._lastRawTimeLeft = -1;
+      this._lastTimeLeft = -1;
+      this._details = "";
+    } else {
+      // Compute the new time left only if state actually changed.
+      if (this._lastRawTimeLeft != summary.rawTimeLeft) {
+        this._lastRawTimeLeft = summary.rawTimeLeft;
+        this._lastTimeLeft = DownloadsCommon.smoothSeconds(summary.rawTimeLeft,
+                                                           this._lastTimeLeft);
+      }
+      [this._details] = DownloadUtils.getDownloadStatusNoRate(
+        summary.totalTransferred, summary.totalSize, summary.slowestSpeed,
+        this._lastTimeLeft);
+    }
+  },
+}
diff --git a/browser/components/downloads/DownloadsTaskbar.jsm b/browser/components/downloads/DownloadsTaskbar.jsm
new file mode 100644
index 000000000..cf915abb5
--- /dev/null
+++ b/browser/components/downloads/DownloadsTaskbar.jsm
@@ -0,0 +1,177 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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/. */
+
+/**
+ * Handles the download progress indicator in the taskbar.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "DownloadsTaskbar",
+];
+
+////////////////////////////////////////////////////////////////////////////////
+//// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
+                                  "resource://gre/modules/Downloads.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "RecentWindow",
+                                  "resource:///modules/RecentWindow.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Services",
+                                  "resource://gre/modules/Services.jsm");
+
+XPCOMUtils.defineLazyGetter(this, "gWinTaskbar", function () {
+  if (!("@mozilla.org/windows-taskbar;1" in Cc)) {
+    return null;
+  }
+  let winTaskbar = Cc["@mozilla.org/windows-taskbar;1"]
+                     .getService(Ci.nsIWinTaskbar);
+  return winTaskbar.available && winTaskbar;
+});
+
+XPCOMUtils.defineLazyGetter(this, "gMacTaskbarProgress", function () {
+  return ("@mozilla.org/widget/macdocksupport;1" in Cc) &&
+         Cc["@mozilla.org/widget/macdocksupport;1"]
+           .getService(Ci.nsITaskbarProgress);
+});
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsTaskbar
+
+/**
+ * Handles the download progress indicator in the taskbar.
+ */
+this.DownloadsTaskbar = {
+  /**
+   * Underlying DownloadSummary providing the aggregate download information, or
+   * null if the indicator has never been initialized.
+   */
+  _summary: null,
+
+  /**
+   * nsITaskbarProgress object to which download information is dispatched.
+   * This can be null if the indicator has never been initialized or if the
+   * indicator is currently hidden on Windows.
+   */
+  _taskbarProgress: null,
+
+  /**
+   * This method is called after a new browser window is opened, and ensures
+   * that the download progress indicator is displayed in the taskbar.
+   *
+   * On Windows, the indicator is attached to the first browser window that
+   * calls this method.  When the window is closed, the indicator is moved to
+   * another browser window, if available, in no particular order.  When there
+   * are no browser windows visible, the indicator is hidden.
+   *
+   * On Mac OS X, the indicator is initialized globally when this method is
+   * called for the first time.  Subsequent calls have no effect.
+   *
+   * @param aBrowserWindow
+   *        nsIDOMWindow object of the newly opened browser window to which the
+   *        indicator may be attached.
+   */
+  registerIndicator(aBrowserWindow) {
+    if (!this._taskbarProgress) {
+      if (gMacTaskbarProgress) {
+        // On Mac OS X, we have to register the global indicator only once.
+        this._taskbarProgress = gMacTaskbarProgress;
+        // Free the XPCOM reference on shutdown, to prevent detecting a leak.
+        Services.obs.addObserver(() => {
+          this._taskbarProgress = null;
+          gMacTaskbarProgress = null;
+        }, "quit-application-granted", false);
+      } else if (gWinTaskbar) {
+        // On Windows, the indicator is currently hidden because we have no
+        // previous browser window, thus we should attach the indicator now.
+        this._attachIndicator(aBrowserWindow);
+      } else {
+        // The taskbar indicator is not available on this platform.
+        return;
+      }
+    }
+
+    // Ensure that the DownloadSummary object will be created asynchronously.
+    if (!this._summary) {
+      Downloads.getSummary(Downloads.ALL).then(summary => {
+        // In case the method is re-entered, we simply ignore redundant
+        // invocations of the callback, instead of keeping separate state.
+        if (this._summary) {
+          return;
+        }
+        this._summary = summary;
+        return this._summary.addView(this);
+      }).then(null, Cu.reportError);
+    }
+  },
+
+  /**
+   * On Windows, attaches the taskbar indicator to the specified browser window.
+   */
+  _attachIndicator(aWindow) {
+    // Activate the indicator on the specified window.
+    let docShell = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                          .getInterface(Ci.nsIWebNavigation)
+                          .QueryInterface(Ci.nsIDocShellTreeItem).treeOwner
+                          .QueryInterface(Ci.nsIInterfaceRequestor)
+                          .getInterface(Ci.nsIXULWindow).docShell;
+    this._taskbarProgress = gWinTaskbar.getTaskbarProgress(docShell);
+
+    // If the DownloadSummary object has already been created, we should update
+    // the state of the new indicator, otherwise it will be updated as soon as
+    // the DownloadSummary view is registered.
+    if (this._summary) {
+      this.onSummaryChanged();
+    }
+
+    aWindow.addEventListener("unload", () => {
+      // Locate another browser window, excluding the one being closed.
+      let browserWindow = RecentWindow.getMostRecentBrowserWindow();
+      if (browserWindow) {
+        // Move the progress indicator to the other browser window.
+        this._attachIndicator(browserWindow);
+      } else {
+        // The last browser window has been closed.  We remove the reference to
+        // the taskbar progress object so that the indicator will be registered
+        // again on the next browser window that is opened.
+        this._taskbarProgress = null;
+      }
+    }, false);
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// DownloadSummary view
+
+  onSummaryChanged() {
+    // If the last browser window has been closed, we have no indicator any more.
+    if (!this._taskbarProgress) {
+      return;
+    }
+
+    if (this._summary.allHaveStopped || this._summary.progressTotalBytes == 0) {
+      this._taskbarProgress.setProgressState(
+                               Ci.nsITaskbarProgress.STATE_NO_PROGRESS, 0, 0);
+    } else {
+      // For a brief moment before completion, some download components may
+      // report more transferred bytes than the total number of bytes.  Thus,
+      // ensure that we never break the expectations of the progress indicator.
+      let progressCurrentBytes = Math.min(this._summary.progressTotalBytes,
+                                          this._summary.progressCurrentBytes);
+      this._taskbarProgress.setProgressState(
+                               Ci.nsITaskbarProgress.STATE_NORMAL,
+                               progressCurrentBytes,
+                               this._summary.progressTotalBytes);
+    }
+  },
+};
diff --git a/browser/components/downloads/DownloadsViewUI.jsm b/browser/components/downloads/DownloadsViewUI.jsm
new file mode 100644
index 000000000..3b0e4c1b7
--- /dev/null
+++ b/browser/components/downloads/DownloadsViewUI.jsm
@@ -0,0 +1,395 @@
+/* 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/. */
+
+/*
+ * This module is imported by code that uses the "download.xml" binding, and
+ * provides prototypes for objects that handle input and display information.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "DownloadsViewUI",
+];
+
+const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
+                                  "resource://gre/modules/Downloads.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadUtils",
+                                  "resource://gre/modules/DownloadUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadsCommon",
+                                  "resource:///modules/DownloadsCommon.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm");
+
+this.DownloadsViewUI = {
+  /**
+   * Returns true if the given string is the name of a command that can be
+   * handled by the Downloads user interface, including standard commands.
+   */
+  isCommandName(name) {
+    return name.startsWith("cmd_") || name.startsWith("downloadsCmd_");
+  },
+};
+
+/**
+ * A download element shell is responsible for handling the commands and the
+ * displayed data for a single element that uses the "download.xml" binding.
+ *
+ * The information to display is obtained through the associated Download object
+ * from the JavaScript API for downloads, and commands are executed using a
+ * combination of Download methods and DownloadsCommon.jsm helper functions.
+ *
+ * Specialized versions of this shell must be defined, and they are required to
+ * implement the "download" property or getter. Currently these objects are the
+ * HistoryDownloadElementShell and the DownloadsViewItem for the panel. The
+ * history view may use a HistoryDownload object in place of a Download object.
+ */
+this.DownloadsViewUI.DownloadElementShell = function () {}
+
+this.DownloadsViewUI.DownloadElementShell.prototype = {
+  /**
+   * The richlistitem for the download, initialized by the derived object.
+   */
+  element: null,
+
+  /**
+   * URI string for the file type icon displayed in the download element.
+   */
+  get image() {
+    if (!this.download.target.path) {
+      // Old history downloads may not have a target path.
+      return "moz-icon://.unknown?size=32";
+    }
+
+    // When a download that was previously in progress finishes successfully, it
+    // means that the target file now exists and we can extract its specific
+    // icon, for example from a Windows executable. To ensure that the icon is
+    // reloaded, however, we must change the URI used by the XUL image element,
+    // for example by adding a query parameter. This only works if we add one of
+    // the parameters explicitly supported by the nsIMozIconURI interface.
+    return "moz-icon://" + this.download.target.path + "?size=32" +
+           (this.download.succeeded ? "&state=normal" : "");
+  },
+
+  /**
+   * The user-facing label for the download. This is normally the leaf name of
+   * the download target file. In case this is a very old history download for
+   * which the target file is unknown, the download source URI is displayed.
+   */
+  get displayName() {
+    if (!this.download.target.path) {
+      return this.download.source.url;
+    }
+    return OS.Path.basename(this.download.target.path);
+  },
+
+  /**
+   * The progress element for the download, or undefined in case the XBL binding
+   * has not been applied yet.
+   */
+  get _progressElement() {
+    if (!this.__progressElement) {
+      // If the element is not available now, we will try again the next time.
+      this.__progressElement =
+           this.element.ownerDocument.getAnonymousElementByAttribute(
+                                         this.element, "anonid",
+                                         "progressmeter");
+    }
+    return this.__progressElement;
+  },
+
+  /**
+   * Processes a major state change in the user interface, then proceeds with
+   * the normal progress update. This function is not called for every progress
+   * update in order to improve performance.
+   */
+  _updateState() {
+    this.element.setAttribute("displayName", this.displayName);
+    this.element.setAttribute("image", this.image);
+    this.element.setAttribute("state",
+                              DownloadsCommon.stateOfDownload(this.download));
+
+    if (!this.download.succeeded && this.download.error &&
+        this.download.error.becauseBlockedByReputationCheck) {
+      this.element.setAttribute("verdict",
+                                this.download.error.reputationCheckVerdict);
+    } else {
+      this.element.removeAttribute("verdict");
+    }
+
+    // Since state changed, reset the time left estimation.
+    this.lastEstimatedSecondsLeft = Infinity;
+
+    this._updateProgress();
+  },
+
+  /**
+   * Updates the elements that change regularly for in-progress downloads,
+   * namely the progress bar and the status line.
+   */
+  _updateProgress() {
+    if (this.download.succeeded) {
+      // We only need to add or remove this attribute for succeeded downloads.
+      if (this.download.target.exists) {
+        this.element.setAttribute("exists", "true");
+      } else {
+        this.element.removeAttribute("exists");
+      }
+    }
+
+    // When a block is confirmed, the removal of blocked data will not trigger a
+    // state change for the download, so this class must be updated here.
+    this.element.classList.toggle("temporary-block",
+                                  !!this.download.hasBlockedData);
+
+    // The progress bar is only displayed for in-progress downloads.
+    if (this.download.hasProgress) {
+      this.element.setAttribute("progressmode", "normal");
+      this.element.setAttribute("progress", this.download.progress);
+    } else {
+      this.element.setAttribute("progressmode", "undetermined");
+    }
+
+    if (this.download.stopped && this.download.canceled &&
+        this.download.hasPartialData) {
+      this.element.setAttribute("progresspaused", "true");
+    } else {
+      this.element.removeAttribute("progresspaused");
+    }
+
+    // Dispatch the ValueChange event for accessibility, if possible.
+    if (this._progressElement) {
+      let event = this.element.ownerDocument.createEvent("Events");
+      event.initEvent("ValueChange", true, true);
+      this._progressElement.dispatchEvent(event);
+    }
+
+    let status = this.statusTextAndTip;
+    this.element.setAttribute("status", status.text);
+    this.element.setAttribute("statusTip", status.tip);
+  },
+
+  lastEstimatedSecondsLeft: Infinity,
+
+  /**
+   * Returns the text for the status line and the associated tooltip. These are
+   * returned by a single property because they are computed together. The
+   * result may be overridden by derived objects.
+   */
+  get statusTextAndTip() {
+    return this.rawStatusTextAndTip;
+  },
+
+  /**
+   * Derived objects may call this to get the status text.
+   */
+  get rawStatusTextAndTip() {
+    let s = DownloadsCommon.strings;
+
+    let text = "";
+    let tip = "";
+
+    if (!this.download.stopped) {
+      let totalBytes = this.download.hasProgress ? this.download.totalBytes
+                                                 : -1;
+      // By default, extended status information including the individual
+      // download rate is displayed in the tooltip. The history view overrides
+      // the getter and displays the datails in the main area instead.
+      [text] = DownloadUtils.getDownloadStatusNoRate(
+                                          this.download.currentBytes,
+                                          totalBytes,
+                                          this.download.speed,
+                                          this.lastEstimatedSecondsLeft);
+      let newEstimatedSecondsLeft;
+      [tip, newEstimatedSecondsLeft] = DownloadUtils.getDownloadStatus(
+                                          this.download.currentBytes,
+                                          totalBytes,
+                                          this.download.speed,
+                                          this.lastEstimatedSecondsLeft);
+      this.lastEstimatedSecondsLeft = newEstimatedSecondsLeft;
+    } else if (this.download.canceled && this.download.hasPartialData) {
+      let totalBytes = this.download.hasProgress ? this.download.totalBytes
+                                                 : -1;
+      let transfer = DownloadUtils.getTransferTotal(this.download.currentBytes,
+                                                    totalBytes);
+
+      // We use the same XUL label to display both the state and the amount
+      // transferred, for example "Paused -  1.1 MB".
+      text = s.statusSeparatorBeforeNumber(s.statePaused, transfer);
+    } else if (!this.download.succeeded && !this.download.canceled &&
+               !this.download.error) {
+      text = s.stateStarting;
+    } else {
+      let stateLabel;
+
+      if (this.download.succeeded) {
+        // For completed downloads, show the file size (e.g. "1.5 MB").
+        if (this.download.target.size !== undefined) {
+          let [size, unit] =
+            DownloadUtils.convertByteUnits(this.download.target.size);
+          stateLabel = s.sizeWithUnits(size, unit);
+        } else {
+          // History downloads may not have a size defined.
+          stateLabel = s.sizeUnknown;
+        }
+      } else if (this.download.canceled) {
+        stateLabel = s.stateCanceled;
+      } else if (this.download.error.becauseBlockedByParentalControls) {
+        stateLabel = s.stateBlockedParentalControls;
+      } else if (this.download.error.becauseBlockedByReputationCheck) {
+        stateLabel = this.rawBlockedTitleAndDetails[0];
+      } else {
+        stateLabel = s.stateFailed;
+      }
+
+      let referrer = this.download.source.referrer || this.download.source.url;
+      let [displayHost, fullHost] = DownloadUtils.getURIHost(referrer);
+
+      let date = new Date(this.download.endTime);
+      let [displayDate, fullDate] = DownloadUtils.getReadableDates(date);
+
+      let firstPart = s.statusSeparator(stateLabel, displayHost);
+      text = s.statusSeparator(firstPart, displayDate);
+      tip = s.statusSeparator(fullHost, fullDate);
+    }
+
+    return { text, tip: tip || text };
+  },
+
+  /**
+   * Returns [title, [details1, details2]] for blocked downloads.
+   */
+  get rawBlockedTitleAndDetails() {
+    let s = DownloadsCommon.strings;
+    if (!this.download.error ||
+        !this.download.error.becauseBlockedByReputationCheck) {
+      return [null, null];
+    }
+    switch (this.download.error.reputationCheckVerdict) {
+      case Downloads.Error.BLOCK_VERDICT_UNCOMMON:
+        return [s.blockedUncommon2, [s.unblockTypeUncommon2, s.unblockTip2]];
+      case Downloads.Error.BLOCK_VERDICT_POTENTIALLY_UNWANTED:
+        return [s.blockedPotentiallyUnwanted,
+                [s.unblockTypePotentiallyUnwanted2, s.unblockTip2]];
+      case Downloads.Error.BLOCK_VERDICT_MALWARE:
+        return [s.blockedMalware, [s.unblockTypeMalware, s.unblockTip2]];
+    }
+    throw new Error("Unexpected reputationCheckVerdict: " +
+                    this.download.error.reputationCheckVerdict);
+    // return anyway to avoid a JS strict warning.
+    return [null, null];
+  },
+
+  /**
+   * Shows the appropriate unblock dialog based on the verdict, and executes the
+   * action selected by the user in the dialog, which may involve unblocking,
+   * opening or removing the file.
+   *
+   * @param window
+   *        The window to which the dialog should be anchored.
+   * @param dialogType
+   *        Can be "unblock", "chooseUnblock", or "chooseOpen".
+   */
+  confirmUnblock(window, dialogType) {
+    DownloadsCommon.confirmUnblockDownload({
+      verdict: this.download.error.reputationCheckVerdict,
+      window,
+      dialogType,
+    }).then(action => {
+      if (action == "open") {
+        return this.unblockAndOpenDownload();
+      } else if (action == "unblock") {
+        return this.download.unblock();
+      } else if (action == "confirmBlock") {
+        return this.download.confirmBlock();
+      }
+    }).catch(Cu.reportError);
+  },
+
+  /**
+   * Unblocks the downloaded file and opens it.
+   *
+   * @return A promise that's resolved after the file has been opened.
+   */
+  unblockAndOpenDownload() {
+    return this.download.unblock().then(() => this.downloadsCmd_open());
+  },
+
+  /**
+   * Returns the name of the default command to use for the current state of the
+   * download, when there is a double click or another default interaction. If
+   * there is no default command for the current state, returns an empty string.
+   * The commands are implemented as functions on this object or derived ones.
+   */
+  get currentDefaultCommandName() {
+    switch (DownloadsCommon.stateOfDownload(this.download)) {
+      case Ci.nsIDownloadManager.DOWNLOAD_NOTSTARTED:
+        return "downloadsCmd_cancel";
+      case Ci.nsIDownloadManager.DOWNLOAD_FAILED:
+      case Ci.nsIDownloadManager.DOWNLOAD_CANCELED:
+        return "downloadsCmd_retry";
+      case Ci.nsIDownloadManager.DOWNLOAD_PAUSED:
+        return "downloadsCmd_pauseResume";
+      case Ci.nsIDownloadManager.DOWNLOAD_FINISHED:
+        return "downloadsCmd_open";
+      case Ci.nsIDownloadManager.DOWNLOAD_BLOCKED_PARENTAL:
+        return "downloadsCmd_openReferrer";
+      case Ci.nsIDownloadManager.DOWNLOAD_DIRTY:
+        return "downloadsCmd_showBlockedInfo";
+    }
+    return "";
+  },
+
+  /**
+   * Returns true if the specified command can be invoked on the current item.
+   * The commands are implemented as functions on this object or derived ones.
+   *
+   * @param aCommand
+   *        Name of the command to check, for example "downloadsCmd_retry".
+   */
+  isCommandEnabled(aCommand) {
+    switch (aCommand) {
+      case "downloadsCmd_retry":
+        return this.download.canceled || this.download.error;
+      case "downloadsCmd_pauseResume":
+        return this.download.hasPartialData && !this.download.error;
+      case "downloadsCmd_openReferrer":
+        return !!this.download.source.referrer;
+      case "downloadsCmd_confirmBlock":
+      case "downloadsCmd_chooseUnblock":
+      case "downloadsCmd_chooseOpen":
+      case "downloadsCmd_unblock":
+      case "downloadsCmd_unblockAndOpen":
+        return this.download.hasBlockedData;
+    }
+    return false;
+  },
+
+  downloadsCmd_cancel() {
+    // This is the correct way to avoid race conditions when cancelling.
+    this.download.cancel().catch(() => {});
+    this.download.removePartialData().catch(Cu.reportError);
+  },
+
+  downloadsCmd_retry() {
+    // Errors when retrying are already reported as download failures.
+    this.download.start().catch(() => {});
+  },
+
+  downloadsCmd_pauseResume() {
+    if (this.download.stopped) {
+      this.download.start();
+    } else {
+      this.download.cancel();
+    }
+  },
+
+  downloadsCmd_confirmBlock() {
+    this.download.confirmBlock().catch(Cu.reportError);
+  },
+};
diff --git a/browser/components/downloads/content/allDownloadsViewOverlay.js b/browser/components/downloads/content/allDownloadsViewOverlay.js
new file mode 100644
index 000000000..58078cd08
--- /dev/null
+++ b/browser/components/downloads/content/allDownloadsViewOverlay.js
@@ -0,0 +1,1439 @@
+/* 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/. */
+
+var { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadUtils",
+                                  "resource://gre/modules/DownloadUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadsCommon",
+                                  "resource:///modules/DownloadsCommon.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadsViewUI",
+                                  "resource:///modules/DownloadsViewUI.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+                                  "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+                                  "resource://gre/modules/NetUtil.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
+                                  "resource://gre/modules/PlacesUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "RecentWindow",
+                                  "resource:///modules/RecentWindow.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Services",
+                                  "resource://gre/modules/Services.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+
+const nsIDM = Ci.nsIDownloadManager;
+
+const DESTINATION_FILE_URI_ANNO  = "downloads/destinationFileURI";
+const DOWNLOAD_META_DATA_ANNO    = "downloads/metaData";
+
+/**
+ * Represents a download from the browser history. It implements part of the
+ * interface of the Download object.
+ *
+ * @param aPlacesNode
+ *        The Places node from which the history download should be initialized.
+ */
+function HistoryDownload(aPlacesNode) {
+  // TODO (bug 829201): history downloads should get the referrer from Places.
+  this.source = {
+    url: aPlacesNode.uri,
+  };
+  this.target = {
+    path: undefined,
+    exists: false,
+    size: undefined,
+  };
+
+  // In case this download cannot obtain its end time from the Places metadata,
+  // use the time from the Places node, that is the start time of the download.
+  this.endTime = aPlacesNode.time / 1000;
+}
+
+HistoryDownload.prototype = {
+  /**
+   * Pushes information from Places metadata into this object.
+   */
+  updateFromMetaData(metaData) {
+    try {
+      this.target.path = Cc["@mozilla.org/network/protocol;1?name=file"]
+                           .getService(Ci.nsIFileProtocolHandler)
+                           .getFileFromURLSpec(metaData.targetFileSpec).path;
+    } catch (ex) {
+      this.target.path = undefined;
+    }
+
+    if ("state" in metaData) {
+      this.succeeded = metaData.state == nsIDM.DOWNLOAD_FINISHED;
+      this.canceled = metaData.state == nsIDM.DOWNLOAD_CANCELED ||
+                      metaData.state == nsIDM.DOWNLOAD_PAUSED;
+      this.endTime = metaData.endTime;
+
+      // Recreate partial error information from the state saved in history.
+      if (metaData.state == nsIDM.DOWNLOAD_FAILED) {
+        this.error = { message: "History download failed." };
+      } else if (metaData.state == nsIDM.DOWNLOAD_BLOCKED_PARENTAL) {
+        this.error = { becauseBlockedByParentalControls: true };
+      } else if (metaData.state == nsIDM.DOWNLOAD_DIRTY) {
+        this.error = {
+          becauseBlockedByReputationCheck: true,
+          reputationCheckVerdict: metaData.reputationCheckVerdict || "",
+        };
+      } else {
+        this.error = null;
+      }
+
+      // Normal history downloads are assumed to exist until the user interface
+      // is refreshed, at which point these values may be updated.
+      this.target.exists = true;
+      this.target.size = metaData.fileSize;
+    } else {
+      // Metadata might be missing from a download that has started but hasn't
+      // stopped already. Normally, this state is overridden with the one from
+      // the corresponding in-progress session download. But if the browser is
+      // terminated abruptly and additionally the file with information about
+      // in-progress downloads is lost, we may end up using this state. We use
+      // the failed state to allow the download to be restarted.
+      //
+      // On the other hand, if the download is missing the target file
+      // annotation as well, it is just a very old one, and we can assume it
+      // succeeded.
+      this.succeeded = !this.target.path;
+      this.error = this.target.path ? { message: "Unstarted download." } : null;
+      this.canceled = false;
+
+      // These properties may be updated if the user interface is refreshed.
+      this.target.exists = false;
+      this.target.size = undefined;
+    }
+  },
+
+  /**
+   * History downloads are never in progress.
+   */
+  stopped: true,
+
+  /**
+   * No percentage indication is shown for history downloads.
+   */
+  hasProgress: false,
+
+  /**
+   * History downloads cannot be restarted using their partial data, even if
+   * they are indicated as paused in their Places metadata. The only way is to
+   * use the information from a persisted session download, that will be shown
+   * instead of the history download. In case this session download is not
+   * available, we show the history download as canceled, not paused.
+   */
+  hasPartialData: false,
+
+  /**
+   * This method mimicks the "start" method of session downloads, and is called
+   * when the user retries a history download.
+   *
+   * At present, we always ask the user for a new target path when retrying a
+   * history download. In the future we may consider reusing the known target
+   * path if the folder still exists and the file name is not already used,
+   * except when the user preferences indicate that the target path should be
+   * requested every time a new download is started.
+   */
+  start() {
+    let browserWin = RecentWindow.getMostRecentBrowserWindow();
+    let initiatingDoc = browserWin ? browserWin.document : document;
+
+    // Do not suggest a file name if we don't know the original target.
+    let leafName = this.target.path ? OS.Path.basename(this.target.path) : null;
+    DownloadURL(this.source.url, leafName, initiatingDoc);
+
+    return Promise.resolve();
+  },
+
+  /**
+   * This method mimicks the "refresh" method of session downloads, except that
+   * it cannot notify that the data changed to the Downloads View.
+   */
+  refresh: Task.async(function* () {
+    try {
+      this.target.size = (yield OS.File.stat(this.target.path)).size;
+      this.target.exists = true;
+    } catch (ex) {
+      // We keep the known file size from the metadata, if any.
+      this.target.exists = false;
+    }
+  }),
+};
+
+/**
+ * A download element shell is responsible for handling the commands and the
+ * displayed data for a single download view element.
+ *
+ * The shell may contain a session download, a history download, or both.  When
+ * both a history and a session download are present, the session download gets
+ * priority and its information is displayed.
+ *
+ * On construction, a new richlistitem is created, and can be accessed through
+ * the |element| getter. The shell doesn't insert the item in a richlistbox, the
+ * caller must do it and remove the element when it's no longer needed.
+ *
+ * The caller is also responsible for forwarding status notifications for
+ * session downloads, calling the onStateChanged and onChanged methods.
+ *
+ * @param [optional] aSessionDownload
+ *        The session download, required if aHistoryDownload is not set.
+ * @param [optional] aHistoryDownload
+ *        The history download, required if aSessionDownload is not set.
+ */
+function HistoryDownloadElementShell(aSessionDownload, aHistoryDownload) {
+  this.element = document.createElement("richlistitem");
+  this.element._shell = this;
+
+  this.element.classList.add("download");
+  this.element.classList.add("download-state");
+
+  if (aSessionDownload) {
+    this.sessionDownload = aSessionDownload;
+  }
+  if (aHistoryDownload) {
+    this.historyDownload = aHistoryDownload;
+  }
+}
+
+HistoryDownloadElementShell.prototype = {
+  __proto__: DownloadsViewUI.DownloadElementShell.prototype,
+
+  /**
+   * Manages the "active" state of the shell.  By default all the shells without
+   * a session download are inactive, thus their UI is not updated.  They must
+   * be activated when entering the visible area.  Session downloads are always
+   * active.
+   */
+  ensureActive() {
+    if (!this._active) {
+      this._active = true;
+      this.element.setAttribute("active", true);
+      this._updateUI();
+    }
+  },
+  get active() {
+    return !!this._active;
+  },
+
+  /**
+   * Overrides the base getter to return the Download or HistoryDownload object
+   * for displaying information and executing commands in the user interface.
+   */
+  get download() {
+    return this._sessionDownload || this._historyDownload;
+  },
+
+  _sessionDownload: null,
+  get sessionDownload() {
+    return this._sessionDownload;
+  },
+  set sessionDownload(aValue) {
+    if (this._sessionDownload != aValue) {
+      if (!aValue && !this._historyDownload) {
+        throw new Error("Should always have either a Download or a HistoryDownload");
+      }
+
+      this._sessionDownload = aValue;
+
+      this.ensureActive();
+      this._updateUI();
+    }
+    return aValue;
+  },
+
+  _historyDownload: null,
+  get historyDownload() {
+    return this._historyDownload;
+  },
+  set historyDownload(aValue) {
+    if (this._historyDownload != aValue) {
+      if (!aValue && !this._sessionDownload) {
+        throw new Error("Should always have either a Download or a HistoryDownload");
+      }
+
+      this._historyDownload = aValue;
+
+      // We don't need to update the UI if we had a session data item, because
+      // the places information isn't used in this case.
+      if (!this._sessionDownload) {
+        this._updateUI();
+      }
+    }
+    return aValue;
+  },
+
+  _updateUI() {
+    // There is nothing to do if the item has always been invisible.
+    if (!this.active) {
+      return;
+    }
+
+    // Since the state changed, we may need to check the target file again.
+    this._targetFileChecked = false;
+
+    this._updateState();
+  },
+
+  get statusTextAndTip() {
+    let status = this.rawStatusTextAndTip;
+
+    // The base object would show extended progress information in the tooltip,
+    // but we move this to the main view and never display a tooltip.
+    if (!this.download.stopped) {
+      status.text = status.tip;
+    }
+    status.tip = "";
+
+    return status;
+  },
+
+  onStateChanged() {
+    this._updateState();
+
+    if (this.element.selected) {
+      goUpdateDownloadCommands();
+    } else {
+      // If a state change occurs in an item that is not currently selected,
+      // this is the only command that may be affected.
+      goUpdateCommand("downloadsCmd_clearDownloads");
+    }
+  },
+
+  onChanged() {
+    // This cannot be placed within onStateChanged because
+    // when a download goes from hasBlockedData to !hasBlockedData
+    // it will still remain in the same state.
+    this.element.classList.toggle("temporary-block",
+                                  !!this.download.hasBlockedData);
+    this._updateProgress();
+  },
+
+  isCommandEnabled(aCommand) {
+    // The only valid command for inactive elements is cmd_delete.
+    if (!this.active && aCommand != "cmd_delete") {
+      return false;
+    }
+    switch (aCommand) {
+      case "downloadsCmd_open":
+        // This property is false if the download did not succeed.
+        return this.download.target.exists;
+      case "downloadsCmd_show":
+        // TODO: Bug 827010 - Handle part-file asynchronously.
+        if (this._sessionDownload && this.download.target.partFilePath) {
+          let partFile = new FileUtils.File(this.download.target.partFilePath);
+          if (partFile.exists()) {
+            return true;
+          }
+        }
+
+        // This property is false if the download did not succeed.
+        return this.download.target.exists;
+      case "cmd_delete":
+        // We don't want in-progress downloads to be removed accidentally.
+        return this.download.stopped;
+      case "downloadsCmd_cancel":
+        return !!this._sessionDownload;
+    }
+    return DownloadsViewUI.DownloadElementShell.prototype
+                          .isCommandEnabled.call(this, aCommand);
+  },
+
+  doCommand(aCommand) {
+    if (DownloadsViewUI.isCommandName(aCommand)) {
+      this[aCommand]();
+    }
+  },
+
+  downloadsCmd_open() {
+    let file = new FileUtils.File(this.download.target.path);
+    DownloadsCommon.openDownloadedFile(file, null, window);
+  },
+
+  downloadsCmd_show() {
+    let file = new FileUtils.File(this.download.target.path);
+    DownloadsCommon.showDownloadedFile(file);
+  },
+
+  downloadsCmd_openReferrer() {
+    openURL(this.download.source.referrer);
+  },
+
+  cmd_delete() {
+    if (this._sessionDownload) {
+      DownloadsCommon.removeAndFinalizeDownload(this.download);
+    }
+    if (this._historyDownload) {
+      let uri = NetUtil.newURI(this.download.source.url);
+      PlacesUtils.bhistory.removePage(uri);
+    }
+  },
+
+  downloadsCmd_unblock() {
+    this.confirmUnblock(window, "unblock");
+  },
+
+  downloadsCmd_chooseUnblock() {
+    this.confirmUnblock(window, "chooseUnblock");
+  },
+
+  downloadsCmd_chooseOpen() {
+    this.confirmUnblock(window, "chooseOpen");
+  },
+
+  // Returns whether or not the download handled by this shell should
+  // show up in the search results for the given term.  Both the display
+  // name for the download and the url are searched.
+  matchesSearchTerm(aTerm) {
+    if (!aTerm) {
+      return true;
+    }
+    aTerm = aTerm.toLowerCase();
+    return this.displayName.toLowerCase().includes(aTerm) ||
+           this.download.source.url.toLowerCase().includes(aTerm);
+  },
+
+  // Handles return keypress on the element (the keypress listener is
+  // set in the DownloadsPlacesView object).
+  doDefaultCommand() {
+    let command = this.currentDefaultCommandName;
+    if (command && this.isCommandEnabled(command)) {
+      this.doCommand(command);
+    }
+  },
+
+  /**
+   * This method is called by the outer download view, after the controller
+   * commands have already been updated. In case we did not check for the
+   * existence of the target file already, we can do it now and then update
+   * the commands as needed.
+   */
+  onSelect() {
+    if (!this.active) {
+      return;
+    }
+
+    // If this is a history download for which no target file information is
+    // available, we cannot retrieve information about the target file.
+    if (!this.download.target.path) {
+      return;
+    }
+
+    // Start checking for existence.  This may be done twice if onSelect is
+    // called again before the information is collected.
+    if (!this._targetFileChecked) {
+      this._checkTargetFileOnSelect().catch(Cu.reportError);
+    }
+  },
+
+  _checkTargetFileOnSelect: Task.async(function* () {
+    try {
+      yield this.download.refresh();
+    } finally {
+      // Do not try to check for existence again if this failed once.
+      this._targetFileChecked = true;
+    }
+
+    // Update the commands only if the element is still selected.
+    if (this.element.selected) {
+      goUpdateDownloadCommands();
+    }
+
+    // Ensure the interface has been updated based on the new values. We need to
+    // do this because history downloads can't trigger update notifications.
+    this._updateProgress();
+  }),
+};
+
+/**
+ * Relays commands from the download.xml binding to the selected items.
+ */
+const DownloadsView = {
+  onDownloadCommand(event, command) {
+    goDoCommand(command);
+  },
+
+  onDownloadClick() {},
+};
+
+/**
+ * A Downloads Places View is a places view designed to show a places query
+ * for history downloads alongside the session downloads.
+ *
+ * As we don't use the places controller, some methods implemented by other
+ * places views are not implemented by this view.
+ *
+ * A richlistitem in this view can represent either a past download or a session
+ * download, or both. Session downloads are shown first in the view, and as long
+ * as they exist they "collapses" their history "counterpart" (So we don't show two
+ * items for every download).
+ */
+function DownloadsPlacesView(aRichListBox, aActive = true) {
+  this._richlistbox = aRichListBox;
+  this._richlistbox._placesView = this;
+  window.controllers.insertControllerAt(0, this);
+
+  // Map download URLs to download element shells regardless of their type
+  this._downloadElementsShellsForURI = new Map();
+
+  // Map download data items to their element shells.
+  this._viewItemsForDownloads = new WeakMap();
+
+  // Points to the last session download element. We keep track of this
+  // in order to keep all session downloads above past downloads.
+  this._lastSessionDownloadElement = null;
+
+  this._searchTerm = "";
+
+  this._active = aActive;
+
+  // Register as a downloads view. The places data will be initialized by
+  // the places setter.
+  this._initiallySelectedElement = null;
+  this._downloadsData = DownloadsCommon.getData(window.opener || window);
+  this._downloadsData.addView(this);
+
+  // Get the Download button out of the attention state since we're about to
+  // view all downloads.
+  DownloadsCommon.getIndicatorData(window).attention = DownloadsCommon.ATTENTION_NONE;
+
+  // Make sure to unregister the view if the window is closed.
+  window.addEventListener("unload", () => {
+    window.controllers.removeController(this);
+    this._downloadsData.removeView(this);
+    this.result = null;
+  }, true);
+  // Resizing the window may change items visibility.
+  window.addEventListener("resize", () => {
+    this._ensureVisibleElementsAreActive();
+  }, true);
+}
+
+DownloadsPlacesView.prototype = {
+  get associatedElement() {
+    return this._richlistbox;
+  },
+
+  get active() {
+    return this._active;
+  },
+  set active(val) {
+    this._active = val;
+    if (this._active)
+      this._ensureVisibleElementsAreActive();
+    return this._active;
+  },
+
+  /**
+   * This cache exists in order to optimize the load of the Downloads View, when
+   * Places annotations for history downloads must be read. In fact, annotations
+   * are stored in a single table, and reading all of them at once is much more
+   * efficient than an individual query.
+   *
+   * When this property is first requested, it reads the annotations for all the
+   * history downloads and stores them indefinitely.
+   *
+   * The historical annotations are not expected to change for the duration of
+   * the session, except in the case where a session download is running for the
+   * same URI as a history download. To ensure we don't use stale data, URIs
+   * corresponding to session downloads are permanently removed from the cache.
+   * This is a very small mumber compared to history downloads.
+   *
+   * This property returns a Map from each download source URI found in Places
+   * annotations to an object with the format:
+   *
+   * { targetFileSpec, state, endTime, fileSize, ... }
+   *
+   * The targetFileSpec property is the value of "downloads/destinationFileURI",
+   * while the other properties are taken from "downloads/metaData". Any of the
+   * properties may be missing from the object.
+   */
+  get _cachedPlacesMetaData() {
+    if (!this.__cachedPlacesMetaData) {
+      this.__cachedPlacesMetaData = new Map();
+
+      // Read the metadata annotations first, but ignore invalid JSON.
+      for (let result of PlacesUtils.annotations.getAnnotationsWithName(
+                                                 DOWNLOAD_META_DATA_ANNO)) {
+        try {
+          this.__cachedPlacesMetaData.set(result.uri.spec,
+                                          JSON.parse(result.annotationValue));
+        } catch (ex) {}
+      }
+
+      // Add the target file annotations to the metadata.
+      for (let result of PlacesUtils.annotations.getAnnotationsWithName(
+                                                 DESTINATION_FILE_URI_ANNO)) {
+        let metaData = this.__cachedPlacesMetaData.get(result.uri.spec);
+        if (!metaData) {
+          metaData = {};
+          this.__cachedPlacesMetaData.set(result.uri.spec, metaData);
+        }
+        metaData.targetFileSpec = result.annotationValue;
+      }
+    }
+
+    return this.__cachedPlacesMetaData;
+  },
+  __cachedPlacesMetaData: null,
+
+  /**
+   * Reads current metadata from Places annotations for the specified URI, and
+   * returns an object with the format:
+   *
+   * { targetFileSpec, state, endTime, fileSize, ... }
+   *
+   * The targetFileSpec property is the value of "downloads/destinationFileURI",
+   * while the other properties are taken from "downloads/metaData". Any of the
+   * properties may be missing from the object.
+   */
+  _getPlacesMetaDataFor(spec) {
+    let metaData = {};
+
+    try {
+      let uri = NetUtil.newURI(spec);
+      try {
+        metaData = JSON.parse(PlacesUtils.annotations.getPageAnnotation(
+                                          uri, DOWNLOAD_META_DATA_ANNO));
+      } catch (ex) {}
+      metaData.targetFileSpec = PlacesUtils.annotations.getPageAnnotation(
+                                            uri, DESTINATION_FILE_URI_ANNO);
+    } catch (ex) {}
+
+    return metaData;
+  },
+
+  /**
+   * Given a data item for a session download, or a places node for a past
+   * download, updates the view as necessary.
+   *  1. If the given data is a places node, we check whether there are any
+   *     elements for the same download url. If there are, then we just reset
+   *     their places node. Otherwise we add a new download element.
+   *  2. If the given data is a data item, we first check if there's a history
+   *     download in the list that is not associated with a data item. If we
+   *     found one, we use it for the data item as well and reposition it
+   *     alongside the other session downloads. If we don't, then we go ahead
+   *     and create a new element for the download.
+   *
+   * @param [optional] sessionDownload
+   *        A Download object, or null for history downloads.
+   * @param [optional] aPlacesNode
+   *        The Places node for a history download, or null for session downloads.
+   * @param [optional] aNewest
+   *        @see onDownloadAdded. Ignored for history downloads.
+   * @param [optional] aDocumentFragment
+   *        To speed up the appending of multiple elements to the end of the
+   *        list which are coming in a single batch (i.e. invalidateContainer),
+   *        a document fragment may be passed to which the new elements would
+   *        be appended. It's the caller's job to ensure the fragment is merged
+   *        to the richlistbox at the end.
+   */
+  _addDownloadData(sessionDownload, aPlacesNode, aNewest = false,
+                   aDocumentFragment = null) {
+    let downloadURI = aPlacesNode ? aPlacesNode.uri
+                                  : sessionDownload.source.url;
+    let shellsForURI = this._downloadElementsShellsForURI.get(downloadURI);
+    if (!shellsForURI) {
+      shellsForURI = new Set();
+      this._downloadElementsShellsForURI.set(downloadURI, shellsForURI);
+    }
+
+    // When a session download is attached to a shell, we ensure not to keep
+    // stale metadata around for the corresponding history download. This
+    // prevents stale state from being used if the view is rebuilt.
+    //
+    // Note that we will eagerly load the data in the cache at this point, even
+    // if we have seen no history download. The case where no history download
+    // will appear at all is rare enough in normal usage, so we can apply this
+    // simpler solution rather than keeping a list of cache items to ignore.
+    if (sessionDownload) {
+      this._cachedPlacesMetaData.delete(sessionDownload.source.url);
+    }
+
+    let newOrUpdatedShell = null;
+
+    // Trivial: if there are no shells for this download URI, we always
+    // need to create one.
+    let shouldCreateShell = shellsForURI.size == 0;
+
+    // However, if we do have shells for this download uri, there are
+    // few options:
+    // 1) There's only one shell and it's for a history download (it has
+    //    no data item). In this case, we update this shell and move it
+    //    if necessary
+    // 2) There are multiple shells, indicating multiple downloads for
+    //    the same download uri are running. In this case we create
+    //    another shell for the download (so we have one shell for each data
+    //    item).
+    //
+    // Note: If a cancelled session download is already in the list, and the
+    // download is retried, onDownloadAdded is called again for the same
+    // data item. Thus, we also check that we make sure we don't have a view item
+    // already.
+    if (!shouldCreateShell &&
+        sessionDownload && !this._viewItemsForDownloads.has(sessionDownload)) {
+      // If there's a past-download-only shell for this download-uri with no
+      // associated data item, use it for the new data item. Otherwise, go ahead
+      // and create another shell.
+      shouldCreateShell = true;
+      for (let shell of shellsForURI) {
+        if (!shell.sessionDownload) {
+          shouldCreateShell = false;
+          shell.sessionDownload = sessionDownload;
+          newOrUpdatedShell = shell;
+          this._viewItemsForDownloads.set(sessionDownload, shell);
+          break;
+        }
+      }
+    }
+
+    if (shouldCreateShell) {
+      // If we are adding a new history download here, it means there is no
+      // associated session download, thus we must read the Places metadata,
+      // because it will not be obscured by the session download.
+      let historyDownload = null;
+      if (aPlacesNode) {
+        let metaData = this._cachedPlacesMetaData.get(aPlacesNode.uri) ||
+                       this._getPlacesMetaDataFor(aPlacesNode.uri);
+        historyDownload = new HistoryDownload(aPlacesNode);
+        historyDownload.updateFromMetaData(metaData);
+      }
+      let shell = new HistoryDownloadElementShell(sessionDownload,
+                                                  historyDownload);
+      shell.element._placesNode = aPlacesNode;
+      newOrUpdatedShell = shell;
+      shellsForURI.add(shell);
+      if (sessionDownload) {
+        this._viewItemsForDownloads.set(sessionDownload, shell);
+      }
+    } else if (aPlacesNode) {
+      // We are updating information for a history download for which we have
+      // at least one download element shell already. There are two cases:
+      // 1) There are one or more download element shells for this source URI,
+      //    each with an associated session download. We update the Places node
+      //    because we may need it later, but we don't need to read the Places
+      //    metadata until the last session download is removed.
+      // 2) Occasionally, we may receive a duplicate notification for a history
+      //    download with no associated session download. We have exactly one
+      //    download element shell in this case, but the metdata cannot have
+      //    changed, just the reference to the Places node object is different.
+      // So, we update all the node references and keep the metadata intact.
+      for (let shell of shellsForURI) {
+        if (!shell.historyDownload) {
+          // Create the element to host the metadata when needed.
+          shell.historyDownload = new HistoryDownload(aPlacesNode);
+        }
+        shell.element._placesNode = aPlacesNode;
+      }
+    }
+
+    if (newOrUpdatedShell) {
+      if (aNewest) {
+        this._richlistbox.insertBefore(newOrUpdatedShell.element,
+                                       this._richlistbox.firstChild);
+        if (!this._lastSessionDownloadElement) {
+          this._lastSessionDownloadElement = newOrUpdatedShell.element;
+        }
+        // Some operations like retrying an history download move an element to
+        // the top of the richlistbox, along with other session downloads.
+        // More generally, if a new download is added, should be made visible.
+        this._richlistbox.ensureElementIsVisible(newOrUpdatedShell.element);
+      } else if (sessionDownload) {
+        let before = this._lastSessionDownloadElement ?
+          this._lastSessionDownloadElement.nextSibling : this._richlistbox.firstChild;
+        this._richlistbox.insertBefore(newOrUpdatedShell.element, before);
+        this._lastSessionDownloadElement = newOrUpdatedShell.element;
+      } else {
+        let appendTo = aDocumentFragment || this._richlistbox;
+        appendTo.appendChild(newOrUpdatedShell.element);
+      }
+
+      if (this.searchTerm) {
+        newOrUpdatedShell.element.hidden =
+          !newOrUpdatedShell.element._shell.matchesSearchTerm(this.searchTerm);
+      }
+    }
+
+    // If aDocumentFragment is defined this is a batch change, so it's up to
+    // the caller to append the fragment and activate the visible shells.
+    if (!aDocumentFragment) {
+      this._ensureVisibleElementsAreActive();
+      goUpdateCommand("downloadsCmd_clearDownloads");
+    }
+  },
+
+  _removeElement(aElement) {
+    // If the element was selected exclusively, select its next
+    // sibling first, if not, try for previous sibling, if any.
+    if ((aElement.nextSibling || aElement.previousSibling) &&
+        this._richlistbox.selectedItems &&
+        this._richlistbox.selectedItems.length == 1 &&
+        this._richlistbox.selectedItems[0] == aElement) {
+      this._richlistbox.selectItem(aElement.nextSibling ||
+                                   aElement.previousSibling);
+    }
+
+    if (this._lastSessionDownloadElement == aElement) {
+      this._lastSessionDownloadElement = aElement.previousSibling;
+    }
+
+    this._richlistbox.removeItemFromSelection(aElement);
+    this._richlistbox.removeChild(aElement);
+    this._ensureVisibleElementsAreActive();
+    goUpdateCommand("downloadsCmd_clearDownloads");
+  },
+
+  _removeHistoryDownloadFromView(aPlacesNode) {
+    let downloadURI = aPlacesNode.uri;
+    let shellsForURI = this._downloadElementsShellsForURI.get(downloadURI);
+    if (shellsForURI) {
+      for (let shell of shellsForURI) {
+        if (shell.sessionDownload) {
+          shell.historyDownload = null;
+        } else {
+          this._removeElement(shell.element);
+          shellsForURI.delete(shell);
+          if (shellsForURI.size == 0)
+            this._downloadElementsShellsForURI.delete(downloadURI);
+        }
+      }
+    }
+  },
+
+  _removeSessionDownloadFromView(download) {
+    let shells = this._downloadElementsShellsForURI
+                     .get(download.source.url);
+    if (shells.size == 0) {
+      throw new Error("Should have had at leaat one shell for this uri");
+    }
+
+    let shell = this._viewItemsForDownloads.get(download);
+    if (!shells.has(shell)) {
+      throw new Error("Missing download element shell in shells list for url");
+    }
+
+    // If there's more than one item for this download uri, we can let the
+    // view item for this this particular data item go away.
+    // If there's only one item for this download uri, we should only
+    // keep it if it is associated with a history download.
+    if (shells.size > 1 || !shell.historyDownload) {
+      this._removeElement(shell.element);
+      shells.delete(shell);
+      if (shells.size == 0) {
+        this._downloadElementsShellsForURI.delete(download.source.url);
+      }
+    } else {
+      // We have one download element shell containing both a session download
+      // and a history download, and we are now removing the session download.
+      // Previously, we did not use the Places metadata because it was obscured
+      // by the session download. Since this is no longer the case, we have to
+      // read the latest metadata before removing the session download.
+      let url = shell.historyDownload.source.url;
+      let metaData = this._getPlacesMetaDataFor(url);
+      shell.historyDownload.updateFromMetaData(metaData);
+      shell.sessionDownload = null;
+      // Move it below the session-download items;
+      if (this._lastSessionDownloadElement == shell.element) {
+        this._lastSessionDownloadElement = shell.element.previousSibling;
+      } else {
+        let before = this._lastSessionDownloadElement ?
+          this._lastSessionDownloadElement.nextSibling : this._richlistbox.firstChild;
+        this._richlistbox.insertBefore(shell.element, before);
+      }
+    }
+  },
+
+  _ensureVisibleElementsAreActive() {
+    if (!this.active || this._ensureVisibleTimer ||
+        !this._richlistbox.firstChild) {
+      return;
+    }
+
+    this._ensureVisibleTimer = setTimeout(() => {
+      delete this._ensureVisibleTimer;
+      if (!this._richlistbox.firstChild) {
+        return;
+      }
+
+      let rlbRect = this._richlistbox.getBoundingClientRect();
+      let winUtils = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                           .getInterface(Ci.nsIDOMWindowUtils);
+      let nodes = winUtils.nodesFromRect(rlbRect.left, rlbRect.top,
+                                         0, rlbRect.width, rlbRect.height, 0,
+                                         true, false);
+      // nodesFromRect returns nodes in z-index order, and for the same z-index
+      // sorts them in inverted DOM order, thus starting from the one that would
+      // be on top.
+      let firstVisibleNode, lastVisibleNode;
+      for (let node of nodes) {
+        if (node.localName === "richlistitem" && node._shell) {
+          node._shell.ensureActive();
+          // The first visible node is the last match.
+          firstVisibleNode = node;
+          // While the last visible node is the first match.
+          if (!lastVisibleNode) {
+            lastVisibleNode = node;
+          }
+        }
+      }
+
+      // Also activate the first invisible nodes in both boundaries (that is,
+      // above and below the visible area) to ensure proper keyboard navigation
+      // in both directions.
+      let nodeBelowVisibleArea = lastVisibleNode && lastVisibleNode.nextSibling;
+      if (nodeBelowVisibleArea && nodeBelowVisibleArea._shell) {
+        nodeBelowVisibleArea._shell.ensureActive();
+      }
+
+      let nodeAboveVisibleArea = firstVisibleNode &&
+                                 firstVisibleNode.previousSibling;
+      if (nodeAboveVisibleArea && nodeAboveVisibleArea._shell) {
+        nodeAboveVisibleArea._shell.ensureActive();
+      }
+    }, 10);
+  },
+
+  _place: "",
+  get place() {
+    return this._place;
+  },
+  set place(val) {
+    // Don't reload everything if we don't have to.
+    if (this._place == val) {
+      // XXXmano: places.js relies on this behavior (see Bug 822203).
+      this.searchTerm = "";
+      return val;
+    }
+
+    this._place = val;
+
+    let history = PlacesUtils.history;
+    let queries = { }, options = { };
+    history.queryStringToQueries(val, queries, { }, options);
+    if (!queries.value.length) {
+      queries.value = [history.getNewQuery()];
+    }
+
+    let result = history.executeQueries(queries.value, queries.value.length,
+                                        options.value);
+    result.addObserver(this, false);
+    return val;
+  },
+
+  _result: null,
+  get result() {
+    return this._result;
+  },
+  set result(val) {
+    if (this._result == val) {
+      return val;
+    }
+
+    if (this._result) {
+      this._result.removeObserver(this);
+      this._resultNode.containerOpen = false;
+    }
+
+    if (val) {
+      this._result = val;
+      this._resultNode = val.root;
+      this._resultNode.containerOpen = true;
+      this._ensureInitialSelection();
+    } else {
+      delete this._resultNode;
+      delete this._result;
+    }
+
+    return val;
+  },
+
+  get selectedNodes() {
+    return [for (element of this._richlistbox.selectedItems)
+            if (element._placesNode)
+            element._placesNode];
+  },
+
+  get selectedNode() {
+    let selectedNodes = this.selectedNodes;
+    return selectedNodes.length == 1 ? selectedNodes[0] : null;
+  },
+
+  get hasSelection() {
+    return this.selectedNodes.length > 0;
+  },
+
+  containerStateChanged(aNode, aOldState, aNewState) {
+    this.invalidateContainer(aNode)
+  },
+
+  invalidateContainer(aContainer) {
+    if (aContainer != this._resultNode) {
+      throw new Error("Unexpected container node");
+    }
+    if (!aContainer.containerOpen) {
+      throw new Error("Root container for the downloads query cannot be closed");
+    }
+
+    let suppressOnSelect = this._richlistbox.suppressOnSelect;
+    this._richlistbox.suppressOnSelect = true;
+    try {
+      // Remove the invalidated history downloads from the list and unset the
+      // places node for data downloads.
+      // Loop backwards since _removeHistoryDownloadFromView may removeChild().
+      for (let i = this._richlistbox.childNodes.length - 1; i >= 0; --i) {
+        let element = this._richlistbox.childNodes[i];
+        if (element._placesNode) {
+          this._removeHistoryDownloadFromView(element._placesNode);
+        }
+      }
+    } finally {
+      this._richlistbox.suppressOnSelect = suppressOnSelect;
+    }
+
+    if (aContainer.childCount > 0) {
+      let elementsToAppendFragment = document.createDocumentFragment();
+      for (let i = 0; i < aContainer.childCount; i++) {
+        try {
+          this._addDownloadData(null, aContainer.getChild(i), false,
+                                elementsToAppendFragment);
+        } catch (ex) {
+          Cu.reportError(ex);
+        }
+      }
+
+      // _addDownloadData may not add new elements if there were already
+      // data items in place.
+      if (elementsToAppendFragment.firstChild) {
+        this._appendDownloadsFragment(elementsToAppendFragment);
+        this._ensureVisibleElementsAreActive();
+      }
+    }
+
+    goUpdateDownloadCommands();
+  },
+
+  _appendDownloadsFragment(aDOMFragment) {
+    // Workaround multiple reflows hang by removing the richlistbox
+    // and adding it back when we're done.
+
+    // Hack for bug 836283: reset xbl fields to their old values after the
+    // binding is reattached to avoid breaking the selection state
+    let xblFields = new Map();
+    for (let key of Object.getOwnPropertyNames(this._richlistbox)) {
+      let value = this._richlistbox[key];
+      xblFields.set(key, value);
+    }
+
+    let parentNode = this._richlistbox.parentNode;
+    let nextSibling = this._richlistbox.nextSibling;
+    parentNode.removeChild(this._richlistbox);
+    this._richlistbox.appendChild(aDOMFragment);
+    parentNode.insertBefore(this._richlistbox, nextSibling);
+
+    for (let [key, value] of xblFields) {
+      this._richlistbox[key] = value;
+    }
+  },
+
+  nodeInserted(aParent, aPlacesNode) {
+    this._addDownloadData(null, aPlacesNode);
+  },
+
+  nodeRemoved(aParent, aPlacesNode, aOldIndex) {
+    this._removeHistoryDownloadFromView(aPlacesNode);
+  },
+
+  nodeAnnotationChanged() {},
+  nodeIconChanged() {},
+  nodeTitleChanged() {},
+  nodeKeywordChanged() {},
+  nodeDateAddedChanged() {},
+  nodeLastModifiedChanged() {},
+  nodeHistoryDetailsChanged() {},
+  nodeTagsChanged() {},
+  sortingChanged() {},
+  nodeMoved() {},
+  nodeURIChanged() {},
+  batching() {},
+
+  get controller() {
+    return this._richlistbox.controller;
+  },
+
+  get searchTerm() {
+    return this._searchTerm;
+  },
+  set searchTerm(aValue) {
+    if (this._searchTerm != aValue) {
+      for (let element of this._richlistbox.childNodes) {
+        element.hidden = !element._shell.matchesSearchTerm(aValue);
+      }
+      this._ensureVisibleElementsAreActive();
+    }
+    return this._searchTerm = aValue;
+  },
+
+  /**
+   * When the view loads, we want to select the first item.
+   * However, because session downloads, for which the data is loaded
+   * asynchronously, always come first in the list, and because the list
+   * may (or may not) already contain history downloads at that point, it
+   * turns out that by the time we can select the first item, the user may
+   * have already started using the view.
+   * To make things even more complicated, in other cases, the places data
+   * may be loaded after the session downloads data.  Thus we cannot rely on
+   * the order in which the data comes in.
+   * We work around this by attempting to select the first element twice,
+   * once after the places data is loaded and once when the session downloads
+   * data is done loading.  However, if the selection has changed in-between,
+   * we assume the user has already started using the view and give up.
+   */
+  _ensureInitialSelection() {
+    // Either they're both null, or the selection has not changed in between.
+    if (this._richlistbox.selectedItem == this._initiallySelectedElement) {
+      let firstDownloadElement = this._richlistbox.firstChild;
+      if (firstDownloadElement != this._initiallySelectedElement) {
+        // We may be called before _ensureVisibleElementsAreActive,
+        // or before the download binding is attached. Therefore, ensure the
+        // first item is activated, and pass the item to the richlistbox
+        // setters only at a point we know for sure the binding is attached.
+        firstDownloadElement._shell.ensureActive();
+        Services.tm.mainThread.dispatch(() => {
+          this._richlistbox.selectedItem = firstDownloadElement;
+          this._richlistbox.currentItem = firstDownloadElement;
+          this._initiallySelectedElement = firstDownloadElement;
+        }, Ci.nsIThread.DISPATCH_NORMAL);
+      }
+    }
+  },
+
+  onDataLoadStarting() {},
+  onDataLoadCompleted() {
+    this._ensureInitialSelection();
+  },
+
+  onDownloadAdded(download, newest) {
+    this._addDownloadData(download, null, newest);
+  },
+
+  onDownloadStateChanged(download) {
+    this._viewItemsForDownloads.get(download).onStateChanged();
+  },
+
+  onDownloadChanged(download) {
+    this._viewItemsForDownloads.get(download).onChanged();
+  },
+
+  onDownloadRemoved(download) {
+    this._removeSessionDownloadFromView(download);
+  },
+
+  // nsIController
+  supportsCommand(aCommand) {
+    // Firstly, determine if this is a command that we can handle.
+    if (!DownloadsViewUI.isCommandName(aCommand)) {
+      return false;
+    }
+    if (!(aCommand in this) &&
+        !(aCommand in HistoryDownloadElementShell.prototype)) {
+      return false;
+    }
+    // If this function returns true, other controllers won't get a chance to
+    // process the command even if isCommandEnabled returns false, so it's
+    // important to check if the list is focused here to handle common commands
+    // like copy and paste correctly. The clear downloads command, instead, is
+    // specific to the downloads list but can be invoked from the toolbar, so we
+    // can just return true unconditionally.
+    return aCommand == "downloadsCmd_clearDownloads" ||
+           document.activeElement == this._richlistbox;
+  },
+
+  // nsIController
+  isCommandEnabled(aCommand) {
+    switch (aCommand) {
+      case "cmd_copy":
+        return this._richlistbox.selectedItems.length > 0;
+      case "cmd_selectAll":
+        return true;
+      case "cmd_paste":
+        return this._canDownloadClipboardURL();
+      case "downloadsCmd_clearDownloads":
+        return this._canClearDownloads();
+      default:
+        return Array.every(this._richlistbox.selectedItems,
+                           element => element._shell.isCommandEnabled(aCommand));
+    }
+  },
+
+  _canClearDownloads() {
+    // Downloads can be cleared if there's at least one removable download in
+    // the list (either a history download or a completed session download).
+    // Because history downloads are always removable and are listed after the
+    // session downloads, check from bottom to top.
+    for (let elt = this._richlistbox.lastChild; elt; elt = elt.previousSibling) {
+      // Stopped, paused, and failed downloads with partial data are removed.
+      let download = elt._shell.download;
+      if (download.stopped && !(download.canceled && download.hasPartialData)) {
+        return true;
+      }
+    }
+    return false;
+  },
+
+  _copySelectedDownloadsToClipboard() {
+    let urls = [for (element of this._richlistbox.selectedItems)
+                element._shell.download.source.url];
+
+    Cc["@mozilla.org/widget/clipboardhelper;1"]
+      .getService(Ci.nsIClipboardHelper)
+      .copyString(urls.join("\n"));
+  },
+
+  _getURLFromClipboardData() {
+    let trans = Cc["@mozilla.org/widget/transferable;1"].
+                createInstance(Ci.nsITransferable);
+    trans.init(null);
+
+    let flavors = ["text/x-moz-url", "text/unicode"];
+    flavors.forEach(trans.addDataFlavor);
+
+    Services.clipboard.getData(trans, Services.clipboard.kGlobalClipboard);
+
+    // Getting the data or creating the nsIURI might fail.
+    try {
+      let data = {};
+      trans.getAnyTransferData({}, data, {});
+      let [url, name] = data.value.QueryInterface(Ci.nsISupportsString)
+                            .data.split("\n");
+      if (url) {
+        return [NetUtil.newURI(url, null, null).spec, name];
+      }
+    } catch (ex) {}
+
+    return ["", ""];
+  },
+
+  _canDownloadClipboardURL() {
+    let [url, name] = this._getURLFromClipboardData();
+    return url != "";
+  },
+
+  _downloadURLFromClipboard() {
+    let [url, name] = this._getURLFromClipboardData();
+    let browserWin = RecentWindow.getMostRecentBrowserWindow();
+    let initiatingDoc = browserWin ? browserWin.document : document;
+    DownloadURL(url, name, initiatingDoc);
+  },
+
+  // nsIController
+  doCommand(aCommand) {
+    // Commands may be invoked with keyboard shortcuts even if disabled.
+    if (!this.isCommandEnabled(aCommand)) {
+      return;
+    }
+
+    // If this command is not selection-specific, execute it.
+    if (aCommand in this) {
+      this[aCommand]();
+      return;
+    }
+
+    // Cloning the nodelist into an array to get a frozen list of selected items.
+    // Otherwise, the selectedItems nodelist is live and doCommand may alter the
+    // selection while we are trying to do one particular action, like removing
+    // items from history.
+    let selectedElements = [...this._richlistbox.selectedItems];
+    for (let element of selectedElements) {
+      element._shell.doCommand(aCommand);
+    }
+  },
+
+  // nsIController
+  onEvent() {},
+
+  cmd_copy() {
+    this._copySelectedDownloadsToClipboard();
+  },
+
+  cmd_selectAll() {
+    this._richlistbox.selectAll();
+  },
+
+  cmd_paste() {
+    this._downloadURLFromClipboard();
+  },
+
+  downloadsCmd_clearDownloads() {
+    this._downloadsData.removeFinished();
+    if (this.result) {
+      Cc["@mozilla.org/browser/download-history;1"]
+        .getService(Ci.nsIDownloadHistory)
+        .removeAllDownloads();
+    }
+    // There may be no selection or focus change as a result
+    // of these change, and we want the command updated immediately.
+    goUpdateCommand("downloadsCmd_clearDownloads");
+  },
+
+  onContextMenu(aEvent) {
+    let element = this._richlistbox.selectedItem;
+    if (!element || !element._shell) {
+      return false;
+    }
+
+    // Set the state attribute so that only the appropriate items are displayed.
+    let contextMenu = document.getElementById("downloadsContextMenu");
+    let download = element._shell.download;
+    contextMenu.setAttribute("state",
+                             DownloadsCommon.stateOfDownload(download));
+    contextMenu.classList.toggle("temporary-block",
+                                 !!download.hasBlockedData);
+
+    if (!download.stopped) {
+      // The hasPartialData property of a download may change at any time after
+      // it has started, so ensure we update the related command now.
+      goUpdateCommand("downloadsCmd_pauseResume");
+    }
+
+    return true;
+  },
+
+  onKeyPress(aEvent) {
+    let selectedElements = this._richlistbox.selectedItems;
+    if (aEvent.keyCode == KeyEvent.DOM_VK_RETURN) {
+      // In the content tree, opening bookmarks by pressing return is only
+      // supported when a single item is selected. To be consistent, do the
+      // same here.
+      if (selectedElements.length == 1) {
+        let element = selectedElements[0];
+        if (element._shell) {
+          element._shell.doDefaultCommand();
+        }
+      }
+    }
+    else if (aEvent.charCode == " ".charCodeAt(0)) {
+      // Pause/Resume every selected download
+      for (let element of selectedElements) {
+        if (element._shell.isCommandEnabled("downloadsCmd_pauseResume")) {
+          element._shell.doCommand("downloadsCmd_pauseResume");
+        }
+      }
+    }
+  },
+
+  onDoubleClick(aEvent) {
+    if (aEvent.button != 0) {
+      return;
+    }
+
+    let selectedElements = this._richlistbox.selectedItems;
+    if (selectedElements.length != 1) {
+      return;
+    }
+
+    let element = selectedElements[0];
+    if (element._shell) {
+      element._shell.doDefaultCommand();
+    }
+  },
+
+  onScroll() {
+    this._ensureVisibleElementsAreActive();
+  },
+
+  onSelect() {
+    goUpdateDownloadCommands();
+
+    let selectedElements = this._richlistbox.selectedItems;
+    for (let elt of selectedElements) {
+      if (elt._shell) {
+        elt._shell.onSelect();
+      }
+    }
+  },
+
+  onDragStart(aEvent) {
+    // TODO Bug 831358: Support d&d for multiple selection.
+    // For now, we just drag the first element.
+    let selectedItem = this._richlistbox.selectedItem;
+    if (!selectedItem) {
+      return;
+    }
+
+    let targetPath = selectedItem._shell.download.target.path;
+    if (!targetPath) {
+      return;
+    }
+
+    // We must check for existence synchronously because this is a DOM event.
+    let file = new FileUtils.File(targetPath);
+    if (!file.exists()) {
+      return;
+    }
+
+    let dt = aEvent.dataTransfer;
+    dt.mozSetDataAt("application/x-moz-file", file, 0);
+    let url = Services.io.newFileURI(file).spec;
+    dt.setData("text/uri-list", url);
+    dt.setData("text/plain", url);
+    dt.effectAllowed = "copyMove";
+    dt.addElement(selectedItem);
+  },
+
+  onDragOver(aEvent) {
+    let types = aEvent.dataTransfer.types;
+    if (types.includes("text/uri-list") ||
+        types.includes("text/x-moz-url") ||
+        types.includes("text/plain")) {
+      aEvent.preventDefault();
+    }
+  },
+
+  onDrop(aEvent) {
+    let dt = aEvent.dataTransfer;
+    // If dragged item is from our source, do not try to
+    // redownload already downloaded file.
+    if (dt.mozGetDataAt("application/x-moz-file", 0)) {
+      return;
+    }
+
+    let links = Services.droppedLinkHandler.dropLinks(aEvent);
+    if (!links.length)
+      return;
+    let browserWin = RecentWindow.getMostRecentBrowserWindow();
+    let initiatingDoc = browserWin ? browserWin.document : document;
+    for (let link of links) {
+      if (link.url.startsWith("about:"))
+        continue;
+      DownloadURL(link.url, link.name, initiatingDoc);
+    }
+  },
+};
+
+for (let methodName of ["load", "applyFilter", "selectNode", "selectItems"]) {
+  DownloadsPlacesView.prototype[methodName] = function () {
+    throw new Error("|" + methodName +
+                    "| is not implemented by the downloads view.");
+  }
+}
+
+function goUpdateDownloadCommands() {
+  function updateCommandsForObject(object) {
+    for (let name in object) {
+      if (DownloadsViewUI.isCommandName(name)) {
+        goUpdateCommand(name);
+      }
+    }
+  }
+  updateCommandsForObject(DownloadsPlacesView.prototype);
+  updateCommandsForObject(HistoryDownloadElementShell.prototype);
+}
diff --git a/browser/components/downloads/content/allDownloadsViewOverlay.xul b/browser/components/downloads/content/allDownloadsViewOverlay.xul
new file mode 100644
index 000000000..cb8c699bf
--- /dev/null
+++ b/browser/components/downloads/content/allDownloadsViewOverlay.xul
@@ -0,0 +1,131 @@
+<?xml version="1.0"?>
+
+# 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/.
+
+<?xml-stylesheet href="chrome://browser/content/downloads/downloads.css"?>
+<?xml-stylesheet href="chrome://browser/skin/downloads/allDownloadsViewOverlay.css"?>
+
+<!DOCTYPE overlay [
+<!ENTITY % downloadsDTD SYSTEM "chrome://browser/locale/downloads/downloads.dtd">
+%downloadsDTD;
+]>
+
+<!-- This overlay provides a downloads view that lists both session downloads,
+     using the DownloadsView API, and history downloads, using places queries.
+     The view also implements a command controller and a context menu for
+     managing the downloads list.  In order to use this view:
+     1. Apply this overlay to your window.
+     2. Insert in all the overlay entry-points, namely:
+        <richlistbox id="downloadsRichListBox"/>
+        <commandset id="downloadCommands"/>
+        <menupopup id="downloadsContextMenu"/>
+    3. Make sure your window has the editMenuOverlay overlay applied,
+       because the view implements cmd_copy and cmd_delete.
+    4. Make sure your window has the globalOverlay.js script loaded.
+    5. To initialize the view
+        let view = new DownloadsPlacesView(document.getElementById("downloadsRichListBox"));
+        // This is what the Places Library uses. It could be tweaked a bit as long as the
+        // transition-type is set correctly
+        view.place = "place:transition=7&sort=4";
+-->
+<overlay id="downloadsViewOverlay"
+         xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+
+  <script type="application/javascript"
+          src="chrome://browser/content/downloads/allDownloadsViewOverlay.js"/>
+  <script type="application/javascript"
+          src="chrome://global/content/contentAreaUtils.js"/>
+
+  <richlistbox flex="1"
+               seltype="multiple"
+               id="downloadsRichListBox" context="downloadsContextMenu"
+               onscroll="return this._placesView.onScroll();"
+               onkeypress="return this._placesView.onKeyPress(event);"
+               ondblclick="return this._placesView.onDoubleClick(event);"
+               oncontextmenu="return this._placesView.onContextMenu(event);"
+               ondragstart="this._placesView.onDragStart(event);"
+               ondragover="this._placesView.onDragOver(event);"
+               ondrop="this._placesView.onDrop(event);"
+               onfocus="goUpdateDownloadCommands();"
+               onselect="this._placesView.onSelect();"
+               onblur="goUpdateDownloadCommands();"/>
+
+  <commandset id="downloadCommands"
+              commandupdater="true"
+              events="focus,select,contextmenu"
+              oncommandupdate="goUpdateDownloadCommands();">
+    <command id="downloadsCmd_pauseResume"
+             oncommand="goDoCommand('downloadsCmd_pauseResume')"/>
+    <command id="downloadsCmd_cancel"
+             oncommand="goDoCommand('downloadsCmd_cancel')"/>
+    <command id="downloadsCmd_unblock"
+             oncommand="goDoCommand('downloadsCmd_unblock')"/>
+    <command id="downloadsCmd_chooseUnblock"
+             oncommand="goDoCommand('downloadsCmd_chooseUnblock')"/>
+    <command id="downloadsCmd_chooseOpen"
+             oncommand="goDoCommand('downloadsCmd_chooseOpen')"/>
+    <command id="downloadsCmd_confirmBlock"
+             oncommand="goDoCommand('downloadsCmd_confirmBlock')"/>
+    <command id="downloadsCmd_open"
+             oncommand="goDoCommand('downloadsCmd_open')"/>
+    <command id="downloadsCmd_show"
+             oncommand="goDoCommand('downloadsCmd_show')"/>
+    <command id="downloadsCmd_retry"
+             oncommand="goDoCommand('downloadsCmd_retry')"/>
+    <command id="downloadsCmd_openReferrer"
+             oncommand="goDoCommand('downloadsCmd_openReferrer')"/>
+    <command id="downloadsCmd_clearDownloads"
+             oncommand="goDoCommand('downloadsCmd_clearDownloads')"/>
+  </commandset>
+
+  <menupopup id="downloadsContextMenu" class="download-state">
+    <menuitem command="downloadsCmd_pauseResume"
+              class="downloadPauseMenuItem"
+              label="&cmd.pause.label;"
+              accesskey="&cmd.pause.accesskey;"/>
+    <menuitem command="downloadsCmd_pauseResume"
+              class="downloadResumeMenuItem"
+              label="&cmd.resume.label;"
+              accesskey="&cmd.resume.accesskey;"/>
+    <menuitem command="downloadsCmd_cancel"
+              class="downloadCancelMenuItem"
+              label="&cmd.cancel.label;"
+              accesskey="&cmd.cancel.accesskey;"/>
+    <menuitem command="downloadsCmd_unblock"
+              class="downloadUnblockMenuItem"
+              label="&cmd.unblock2.label;"
+              accesskey="&cmd.unblock2.accesskey;"/>
+    <menuitem command="cmd_delete"
+              class="downloadRemoveFromHistoryMenuItem"
+              label="&cmd.removeFromHistory.label;"
+              accesskey="&cmd.removeFromHistory.accesskey;"/>
+    <menuitem command="downloadsCmd_show"
+              class="downloadShowMenuItem"
+#ifdef XP_MACOSX
+              label="&cmd.showMac.label;"
+              accesskey="&cmd.showMac.accesskey;"
+#else
+              label="&cmd.show.label;"
+              accesskey="&cmd.show.accesskey;"
+#endif
+              />
+
+    <menuseparator class="downloadCommandsSeparator"/>
+
+    <menuitem command="downloadsCmd_openReferrer"
+              label="&cmd.goToDownloadPage.label;"
+              accesskey="&cmd.goToDownloadPage.accesskey;"/>
+    <menuitem command="cmd_copy"
+              label="&cmd.copyDownloadLink.label;"
+              accesskey="&cmd.copyDownloadLink.accesskey;"/>
+
+    <menuseparator/>
+
+    <menuitem command="downloadsCmd_clearDownloads"
+              label="&cmd.clearDownloads.label;"
+              accesskey="&cmd.clearDownloads.accesskey;"/>
+  </menupopup>
+</overlay>
diff --git a/browser/components/downloads/content/contentAreaDownloadsView.css b/browser/components/downloads/content/contentAreaDownloadsView.css
new file mode 100644
index 000000000..abaae1f7b
--- /dev/null
+++ b/browser/components/downloads/content/contentAreaDownloadsView.css
@@ -0,0 +1,11 @@
+/* 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/. */
+
+#downloadsListEmptyDescription {
+  display: none;
+}
+
+#downloadsRichListBox:empty + #downloadsListEmptyDescription {
+  display: -moz-box;
+}
diff --git a/browser/components/downloads/content/contentAreaDownloadsView.js b/browser/components/downloads/content/contentAreaDownloadsView.js
new file mode 100644
index 000000000..6e4f18599
--- /dev/null
+++ b/browser/components/downloads/content/contentAreaDownloadsView.js
@@ -0,0 +1,17 @@
+/* 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/PrivateBrowsingUtils.jsm");
+
+var ContentAreaDownloadsView = {
+  init() {
+    let view = new DownloadsPlacesView(document.getElementById("downloadsRichListBox"));
+    // Do not display the Places downloads in private windows
+    if (!PrivateBrowsingUtils.isContentWindowPrivate(window)) {
+      view.place = "place:transition=7&sort=4";
+    }
+    // Set focus to Downloads list once it is created
+    document.getElementById("downloadsRichListBox").focus();
+  },
+};
diff --git a/browser/components/downloads/content/contentAreaDownloadsView.xul b/browser/components/downloads/content/contentAreaDownloadsView.xul
new file mode 100644
index 000000000..91c986656
--- /dev/null
+++ b/browser/components/downloads/content/contentAreaDownloadsView.xul
@@ -0,0 +1,46 @@
+<?xml version="1.0"?>
+
+# 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/.
+
+<?xml-stylesheet href="chrome://global/skin/"?>
+<?xml-stylesheet href="chrome://browser/content/downloads/contentAreaDownloadsView.css"?>
+<?xml-stylesheet href="chrome://browser/skin/downloads/contentAreaDownloadsView.css"?>
+
+<?xul-overlay href="chrome://browser/content/downloads/allDownloadsViewOverlay.xul"?>
+
+<?xul-overlay href="chrome://global/content/editMenuOverlay.xul"?>
+
+<!DOCTYPE window [
+<!ENTITY % downloadsDTD SYSTEM "chrome://browser/locale/downloads/downloads.dtd">
+%downloadsDTD;
+]>
+
+<window id="contentAreaDownloadsView"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+        title="&downloads.title;"
+        onload="ContentAreaDownloadsView.init();">
+
+  <script type="application/javascript"
+          src="chrome://global/content/globalOverlay.js"/>
+  <script type="application/javascript"
+          src="chrome://browser/content/downloads/contentAreaDownloadsView.js"/>
+
+  <commandset id="editMenuCommands"/>
+
+  <keyset id="editMenuKeys">
+#ifdef XP_MACOSX
+    <key id="key_delete2" keycode="VK_BACK" command="cmd_delete"/>
+#endif
+  </keyset>
+
+  <stack flex="1">
+    <richlistbox id="downloadsRichListBox"/>
+    <description id="downloadsListEmptyDescription"
+                 value="&downloadsListEmpty.label;"
+                 mousethrough="always"/>
+  </stack>
+  <commandset id="downloadCommands"/>
+  <menupopup id="downloadsContextMenu"/>
+</window>
diff --git a/browser/components/downloads/content/download.xml b/browser/components/downloads/content/download.xml
new file mode 100644
index 000000000..29a1530fd
--- /dev/null
+++ b/browser/components/downloads/content/download.xml
@@ -0,0 +1,99 @@
+<?xml version="1.0"?>
+<!-- -*- Mode: HTML; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- -->
+<!-- vim: set ts=2 et sw=2 tw=80: -->
+
+<!-- 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 bindings SYSTEM "chrome://browser/locale/downloads/downloads.dtd">
+
+<bindings id="downloadBindings"
+          xmlns="http://www.mozilla.org/xbl"
+          xmlns:xul="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+          xmlns:xbl="http://www.mozilla.org/xbl">
+
+  <binding id="download"
+           extends="chrome://global/content/bindings/richlistbox.xml#richlistitem">
+    <content orient="horizontal"
+             onclick="DownloadsView.onDownloadClick(event);">
+      <xul:hbox class="downloadMainArea"
+                flex="1"
+                align="center">
+        <xul:stack>
+          <xul:image class="downloadTypeIcon"
+                     validate="always"
+                     xbl:inherits="src=image"/>
+          <xul:image class="downloadBlockedBadge" />
+        </xul:stack>
+        <xul:vbox pack="center"
+                  flex="1"
+                  class="downloadContainer"
+                  style="width: &downloadDetails.width;">
+          <!-- We're letting localizers put a min-width in here primarily
+               because of the downloads summary at the bottom of the list of
+               download items. An element in the summary has the same min-width
+               on a description, and we don't want the panel to change size if the
+               summary isn't being displayed, so we ensure that items share the
+               same minimum width.
+               -->
+          <xul:description class="downloadTarget"
+                           crop="center"
+                           style="min-width: &downloadsSummary.minWidth2;"
+                           xbl:inherits="value=displayName,tooltiptext=displayName"/>
+          <xul:progressmeter anonid="progressmeter"
+                             class="downloadProgress"
+                             min="0"
+                             max="100"
+                             xbl:inherits="mode=progressmode,value=progress,paused=progresspaused"/>
+          <xul:description class="downloadDetails"
+                           crop="end"
+                           xbl:inherits="value=status,tooltiptext=statusTip"/>
+        </xul:vbox>
+      </xul:hbox>
+      <xul:toolbarseparator />
+      <xul:stack class="downloadButtonArea">
+        <xul:button class="downloadButton downloadCancel downloadIconCancel"
+                    tooltiptext="&cmd.cancel.label;"
+                    oncommand="DownloadsView.onDownloadCommand(event, 'downloadsCmd_cancel');"/>
+        <xul:button class="downloadButton downloadRetry downloadIconRetry"
+                    tooltiptext="&cmd.retry.label;"
+                    oncommand="DownloadsView.onDownloadCommand(event, 'downloadsCmd_retry');"/>
+        <xul:button class="downloadButton downloadShow downloadIconShow"
+#ifdef XP_MACOSX
+                    tooltiptext="&cmd.showMac.label;"
+#else
+                    tooltiptext="&cmd.show.label;"
+#endif
+                    oncommand="DownloadsView.onDownloadCommand(event, 'downloadsCmd_show');"/>
+        <xul:button class="downloadButton downloadConfirmBlock downloadIconCancel"
+                    tooltiptext="&cmd.removeFile.label;"
+                    oncommand="DownloadsView.onDownloadCommand(event, 'downloadsCmd_confirmBlock');"/>
+        <xul:button class="downloadButton downloadChooseUnblock downloadIconShow"
+                    tooltiptext="&cmd.chooseUnblock.label;"
+                    oncommand="DownloadsView.onDownloadCommand(event, 'downloadsCmd_chooseUnblock');"/>
+        <xul:button class="downloadButton downloadChooseOpen downloadIconShow"
+                    tooltiptext="&cmd.chooseOpen.label;"
+                    oncommand="DownloadsView.onDownloadCommand(event, 'downloadsCmd_chooseOpen');"/>
+        <xul:button class="downloadButton downloadShowBlockedInfo"
+                    tooltiptext="&cmd.chooseUnblock.label;"
+                    oncommand="DownloadsView.onDownloadCommand(event, 'downloadsCmd_showBlockedInfo');"/>
+      </xul:stack>
+    </content>
+  </binding>
+
+  <binding id="download-toolbarbutton"
+           extends="chrome://global/content/bindings/toolbarbutton.xml#toolbarbutton-badged">
+    <content>
+      <xul:stack class="toolbarbutton-badge-stack">
+        <children />
+        <xul:image class="toolbarbutton-icon" xbl:inherits="validate,src=image,label,consumeanchor"/>
+        <xul:label class="toolbarbutton-badge" xbl:inherits="value=badge" top="0" end="0" crop="none"/>
+      </xul:stack>
+      <xul:label class="toolbarbutton-text" crop="right" flex="1"
+                 xbl:inherits="value=label,accesskey,crop,wrap"/>
+      <xul:label class="toolbarbutton-multiline-text" flex="1"
+                 xbl:inherits="xbl:text=label,accesskey,wrap"/>
+    </content>
+  </binding>
+</bindings>
diff --git a/browser/components/downloads/content/downloads.css b/browser/components/downloads/content/downloads.css
new file mode 100644
index 000000000..dd47c6f91
--- /dev/null
+++ b/browser/components/downloads/content/downloads.css
@@ -0,0 +1,267 @@
+/* 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/. */
+
+/*** Downloads Panel ***/
+
+richlistitem[type="download"] {
+  -moz-binding: url('chrome://browser/content/downloads/download.xml#download');
+}
+
+richlistitem[type="download"]:not([selected]) button {
+  /* Only focus buttons in the selected item. */
+  -moz-user-focus: none;
+}
+
+.downloadsHideDropmarker > #downloadsFooterButtonsSplitter,
+.downloadsHideDropmarker > #downloadsFooterDropmarker {
+  display: none;
+}
+
+richlistitem[type="download"].download-state[state="1"]:not([exists]) > .downloadButtonArea,
+richlistitem[type="download"].download-state[state="1"]:not([exists]) > toolbarseparator {
+  display: none;
+}
+
+#downloadsSummary:not([inprogress]) > vbox > #downloadsSummaryProgress,
+#downloadsSummary:not([inprogress]) > vbox > #downloadsSummaryDetails,
+#downloadsFooter:not([showingsummary]) #downloadsSummary {
+  display: none;
+}
+
+#downloadsFooter[showingdropdown] > stack > #downloadsSummary,
+#downloadsFooter[showingsummary] > stack:hover > #downloadsSummary,
+#downloadsFooter[showingsummary]:not([showingdropdown]) > stack:not(:hover) > #downloadsFooterButtons {
+  /* If we used "visibility: hidden;" then the mouseenter event of
+     #downloadsHistory wouldn't be triggered immediately, and the hover styling
+     of the button would not apply until the mouse is moved again.
+
+     "-moz-user-focus: ignore;" prevents the elements with "opacity: 0;" from
+     being focused with the keyboard. */
+  opacity: 0;
+  -moz-user-focus: ignore;
+}
+
+/*** Downloads View ***/
+
+/**
+ * The downloads richlistbox may list thousands of items, and it turns out
+ * XBL binding attachment, and even more so detachment, is a performance hog.
+ * This hack makes sure we don't apply any binding to inactive items (inactive
+ * items are history downloads that haven't been in the visible area).
+ * We can do this because the richlistbox implementation does not interact
+ * much with the richlistitem binding.  However, this may turn out to have
+ * some side effects (see bug 828111 for the details).
+ *
+ * We might be able to do away with this workaround once bug 653881 is fixed.
+ */
+richlistitem.download {
+  -moz-binding: none;
+}
+
+richlistitem.download[active] {
+  -moz-binding: url("chrome://browser/content/downloads/download.xml#download");
+}
+
+richlistitem.download button {
+  /* These buttons should never get focus, as that would "disable"
+     the downloads view controller (it's only used when the richlistbox
+     is focused). */
+  -moz-user-focus: none;
+}
+
+/*** Visibility of controls inside download items ***/
+.download-state:not(:-moz-any([state="6"], /* Blocked (parental) */
+                              [state="8"], /* Blocked (dirty)    */
+                              [state="9"]) /* Blocked (policy)   */)
+                                           .downloadBlockedBadge,
+
+.download-state:not(:-moz-any([state="-1"],/* Starting (initial) */
+                              [state="5"], /* Starting (queued)  */
+                              [state="0"], /* Downloading        */
+                              [state="4"], /* Paused             */
+                              [state="7"]) /* Scanning           */)
+                                           .downloadProgress,
+
+.download-state:not(          [state="0"]  /* Downloading        */)
+                                           .downloadPauseMenuItem,
+
+.download-state:not(          [state="4"]  /* Paused             */)
+                                           .downloadResumeMenuItem,
+
+/* Blocked (dirty) downloads that have not been confirmed and
+   have temporary data. */
+.download-state:not(          [state="8"]  /* Blocked (dirty)    */)
+                                           .downloadUnblockMenuItem,
+.download-state[state="8"]:not(.temporary-block)
+                                           .downloadUnblockMenuItem,
+
+.download-state:not(:-moz-any([state="2"], /* Failed             */
+                              [state="4"]) /* Paused             */)
+                                           .downloadCancelMenuItem,
+
+.download-state:not(:-moz-any([state="1"], /* Finished           */
+                              [state="2"], /* Failed             */
+                              [state="3"], /* Canceled           */
+                              [state="6"], /* Blocked (parental) */
+                              [state="8"], /* Blocked (dirty)    */
+                              [state="9"]) /* Blocked (policy)   */)
+                                           .downloadRemoveFromHistoryMenuItem,
+
+.download-state:not(:-moz-any([state="-1"],/* Starting (initial) */
+                              [state="0"], /* Downloading        */
+                              [state="1"], /* Finished           */
+                              [state="4"], /* Paused             */
+                              [state="5"]) /* Starting (queued)  */)
+                                           .downloadShowMenuItem,
+
+.download-state[state="7"]                 .downloadCommandsSeparator
+
+{
+  display: none;
+}
+
+/*** Visibility of download buttons ***/
+
+.download-state:not(:-moz-any([state="-1"],/* Starting (initial) */
+                              [state="5"], /* Starting (queued)  */
+                              [state="0"], /* Downloading        */
+                              [state="4"]) /* Paused             */)
+                                           .downloadCancel,
+
+/* Blocked (dirty) downloads that have not been confirmed and
+   have temporary data, for the Malware case. */
+.download-state:not(          [state="8"]  /* Blocked (dirty)    */)
+                                           .downloadConfirmBlock,
+.download-state[state="8"]:not(.temporary-block)
+                                           .downloadConfirmBlock,
+.download-state[state="8"].temporary-block:not([verdict="Malware"])
+                                           .downloadConfirmBlock,
+
+/* Blocked (dirty) downloads that have not been confirmed and
+   have temporary data, for the Potentially Unwanted case. */
+.download-state:not(          [state="8"]  /* Blocked (dirty)    */)
+                                           .downloadChooseUnblock,
+.download-state[state="8"]:not(.temporary-block)
+                                           .downloadChooseUnblock,
+.download-state[state="8"].temporary-block:not([verdict="PotentiallyUnwanted"])
+                                           .downloadChooseUnblock,
+
+/* Blocked (dirty) downloads that have not been confirmed and
+   have temporary data, for the Uncommon case. */
+.download-state:not(          [state="8"]  /* Blocked (dirty)    */)
+                                           .downloadChooseOpen,
+.download-state[state="8"]:not(.temporary-block)
+                                           .downloadChooseOpen,
+.download-state[state="8"].temporary-block:not([verdict="Uncommon"])
+                                           .downloadChooseOpen,
+
+.download-state:not(:-moz-any([state="2"], /* Failed             */
+                              [state="3"]) /* Canceled           */)
+                                           .downloadRetry,
+
+.download-state:not(          [state="1"]  /* Finished           */)
+                                           .downloadShow,
+
+.download-state:-moz-any(     [state="6"], /* Blocked (parental) */
+                              [state="7"], /* Scanning           */
+                              [state="9"]) /* Blocked (policy)   */
+                                           > toolbarseparator,
+
+/* The "show blocked info" button is shown only in the downloads panel. */
+.downloadShowBlockedInfo
+{
+  display: none;
+}
+
+/*** Downloads panel ***/
+
+#downloadsPanel[hasdownloads] #emptyDownloads,
+#downloadsPanel:not([hasdownloads]) #downloadsListBox {
+  display: none;
+}
+
+/*** Downloads panel multiview (main view and blocked-downloads subview) ***/
+
+/* Hide all the usual buttons. */
+#downloadsPanel-mainView .download-state[state="8"] .downloadCancel,
+#downloadsPanel-mainView .download-state[state="8"] .downloadConfirmBlock,
+#downloadsPanel-mainView .download-state[state="8"] .downloadChooseUnblock,
+#downloadsPanel-mainView .download-state[state="8"] .downloadChooseOpen,
+#downloadsPanel-mainView .download-state[state="8"] .downloadRetry,
+#downloadsPanel-mainView .download-state[state="8"] .downloadShow {
+  display: none;
+}
+
+/* Make the panel wide enough to show the download list items without improperly
+   truncating them. */
+#downloadsPanel-multiView > .panel-viewcontainer,
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack,
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack > .panel-mainview {
+  max-width: unset;
+}
+
+/* Show the "show blocked info" button. */
+#downloadsPanel-mainView .download-state[state="8"] .downloadShowBlockedInfo {
+  display: inline;
+}
+
+/** When the main view is showing... **/
+
+/* The subview should be off to the right and not visible at all. */
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype=main] > .panel-subviews {
+  transform: translateX(101%);
+  transition: transform var(--panelui-subview-transition-duration);
+}
+
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype=main] > .panel-subviews:-moz-locale-dir(rtl) {
+  transform: translateX(-101%);
+}
+
+/** When the subview is showing... **/
+
+/* Hide the buttons of all downloads except the one that triggered the
+   subview. */
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype="subview"] .download-state:not([showingsubview]) .downloadButton {
+  visibility: hidden;
+}
+
+/* For the download that triggered the subview, move its button farther to the
+   right by removing padding so that a minimum amount of the main view's right
+   edge needs to be shown. */
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype="subview"] .download-state[showingsubview] {
+  padding: 0;
+}
+
+/* The main view should slide to the left and its right edge should remain
+   visible. */
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype=subview] > .panel-mainview {
+  transform: translateX(calc(-100% + 38px));
+  transition: transform var(--panelui-subview-transition-duration);
+}
+
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype=subview] > .panel-mainview:-moz-locale-dir(rtl) {
+  transform: translateX(calc(100% - 38px));
+}
+
+/* The subview should leave the right edge of the main view uncovered. */
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack > .panel-subviews {
+  /* Use a margin instead of a transform like above so that the subview's width
+     isn't wider than the panel. */
+  -moz-margin-start: 38px !important;
+}
+
+/* Prevent keyboard interaction in the main view by preventing all elements in
+   the main view from being focused... */
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype="subview"] > .panel-mainview #downloadsListBox,
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype="subview"] > .panel-mainview richlistitem,
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype="subview"] > .panel-mainview .downloadButton,
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype="subview"] > .panel-mainview .downloadsPanelFooterButton,
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype="subview"] > .panel-mainview #downloadsSummary {
+  -moz-user-focus: ignore;
+}
+/* ... except for the downloadShowBlockedInfo button in the blocked download.
+   Selecting it with the keyboard should show the main view again. */
+#downloadsPanel-multiView > .panel-viewcontainer > .panel-viewstack[viewtype="subview"] .download-state[showingsubview] .downloadShowBlockedInfo {
+  -moz-user-focus: normal;
+}
diff --git a/browser/components/downloads/content/downloads.js b/browser/components/downloads/content/downloads.js
new file mode 100644
index 000000000..57397c815
--- /dev/null
+++ b/browser/components/downloads/content/downloads.js
@@ -0,0 +1,1732 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/**
+ * Handles the Downloads panel user interface for each browser window.
+ *
+ * This file includes the following constructors and global objects:
+ *
+ * DownloadsPanel
+ * Main entry point for the downloads panel interface.
+ *
+ * DownloadsOverlayLoader
+ * Allows loading the downloads panel and the status indicator interfaces on
+ * demand, to improve startup performance.
+ *
+ * DownloadsView
+ * Builds and updates the downloads list widget, responding to changes in the
+ * download state and real-time data.  In addition, handles part of the user
+ * interaction events raised by the downloads list widget.
+ *
+ * DownloadsViewItem
+ * Builds and updates a single item in the downloads list widget, responding to
+ * changes in the download state and real-time data, and handles the user
+ * interaction events related to a single item in the downloads list widgets.
+ *
+ * DownloadsViewController
+ * Handles part of the user interaction events raised by the downloads list
+ * widget, in particular the "commands" that apply to multiple items, and
+ * dispatches the commands that apply to individual items.
+ */
+
+/**
+ * A few words on focus and focusrings
+ *
+ * We do quite a few hacks in the Downloads Panel for focusrings. In fact, we
+ * basically suppress most if not all XUL-level focusrings, and style/draw
+ * them ourselves (using :focus instead of -moz-focusring). There are a few
+ * reasons for this:
+ *
+ * 1) Richlists on OSX don't have focusrings; instead, they are shown as
+ *    selected. This makes for some ambiguity when we have a focused/selected
+ *    item in the list, and the mouse is hovering a completed download (which
+ *    highlights).
+ * 2) Windows doesn't show focusrings until after the first time that tab is
+ *    pressed (and by then you're focusing the second item in the panel).
+ * 3) Richlistbox sets -moz-focusring even when we select it with a mouse.
+ *
+ * In general, the desired behaviour is to focus the first item after pressing
+ * tab/down, and show that focus with a ring. Then, if the mouse moves over
+ * the panel, to hide that focus ring; essentially resetting us to the state
+ * before pressing the key.
+ *
+ * We end up capturing the tab/down key events, and preventing their default
+ * behaviour. We then set a "keyfocus" attribute on the panel, which allows
+ * us to draw a ring around the currently focused element. If the panel is
+ * closed or the mouse moves over the panel, we remove the attribute.
+ */
+
+"use strict";
+
+var { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadsCommon",
+                                  "resource:///modules/DownloadsCommon.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadsViewUI",
+                                  "resource:///modules/DownloadsViewUI.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+                                  "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+                                  "resource://gre/modules/NetUtil.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
+                                  "resource://gre/modules/PlacesUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Services",
+                                  "resource://gre/modules/Services.jsm");
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsPanel
+
+/**
+ * Main entry point for the downloads panel interface.
+ */
+const DownloadsPanel = {
+  //////////////////////////////////////////////////////////////////////////////
+  //// Initialization and termination
+
+  /**
+   * Internal state of the downloads panel, based on one of the kState
+   * constants.  This is not the same state as the XUL panel element.
+   */
+  _state: 0,
+
+  /** The panel is not linked to downloads data yet. */
+  get kStateUninitialized() {
+    return 0;
+  },
+  /** This object is linked to data, but the panel is invisible. */
+  get kStateHidden() {
+    return 1;
+  },
+  /** The panel will be shown as soon as possible. */
+  get kStateWaitingData() {
+    return 2;
+  },
+  /** The panel is almost shown - we're just waiting to get a handle on the
+      anchor. */
+  get kStateWaitingAnchor() {
+    return 3;
+  },
+  /** The panel is open. */
+  get kStateShown() {
+    return 4;
+  },
+
+  /**
+   * Location of the panel overlay.
+   */
+  get kDownloadsOverlay() {
+    return "chrome://browser/content/downloads/downloadsOverlay.xul";
+  },
+
+  /**
+   * Starts loading the download data in background, without opening the panel.
+   * Use showPanel instead to load the data and open the panel at the same time.
+   *
+   * @param aCallback
+   *        Called when initialization is complete.
+   */
+  initialize(aCallback) {
+    DownloadsCommon.log("Attempting to initialize DownloadsPanel for a window.");
+    if (this._state != this.kStateUninitialized) {
+      DownloadsCommon.log("DownloadsPanel is already initialized.");
+      DownloadsOverlayLoader.ensureOverlayLoaded(this.kDownloadsOverlay,
+                                                 aCallback);
+      return;
+    }
+    this._state = this.kStateHidden;
+
+    window.addEventListener("unload", this.onWindowUnload, false);
+
+    // Load and resume active downloads if required.  If there are downloads to
+    // be shown in the panel, they will be loaded asynchronously.
+    DownloadsCommon.initializeAllDataLinks();
+
+    // Now that data loading has eventually started, load the required XUL
+    // elements and initialize our views.
+    DownloadsCommon.log("Ensuring DownloadsPanel overlay loaded.");
+    DownloadsOverlayLoader.ensureOverlayLoaded(this.kDownloadsOverlay, () => {
+      DownloadsViewController.initialize();
+      DownloadsCommon.log("Attaching DownloadsView...");
+      DownloadsCommon.getData(window).addView(DownloadsView);
+      DownloadsCommon.getSummary(window, DownloadsView.kItemCountLimit)
+                     .addView(DownloadsSummary);
+      DownloadsCommon.log("DownloadsView attached - the panel for this window",
+                          "should now see download items come in.");
+      DownloadsPanel._attachEventListeners();
+      DownloadsCommon.log("DownloadsPanel initialized.");
+      aCallback();
+    });
+  },
+
+  /**
+   * Closes the downloads panel and frees the internal resources related to the
+   * downloads.  The downloads panel can be reopened later, even after this
+   * function has been called.
+   */
+  terminate() {
+    DownloadsCommon.log("Attempting to terminate DownloadsPanel for a window.");
+    if (this._state == this.kStateUninitialized) {
+      DownloadsCommon.log("DownloadsPanel was never initialized. Nothing to do.");
+      return;
+    }
+
+    window.removeEventListener("unload", this.onWindowUnload, false);
+
+    // Ensure that the panel is closed before shutting down.
+    this.hidePanel();
+
+    DownloadsViewController.terminate();
+    DownloadsCommon.getData(window).removeView(DownloadsView);
+    DownloadsCommon.getSummary(window, DownloadsView.kItemCountLimit)
+                   .removeView(DownloadsSummary);
+    this._unattachEventListeners();
+
+    this._state = this.kStateUninitialized;
+
+    DownloadsSummary.active = false;
+    DownloadsCommon.log("DownloadsPanel terminated.");
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Panel interface
+
+  /**
+   * Main panel element in the browser window, or null if the panel overlay
+   * hasn't been loaded yet.
+   */
+  get panel() {
+    // If the downloads panel overlay hasn't loaded yet, just return null
+    // without resetting this.panel.
+    let downloadsPanel = document.getElementById("downloadsPanel");
+    if (!downloadsPanel)
+      return null;
+
+    delete this.panel;
+    return this.panel = downloadsPanel;
+  },
+
+  /**
+   * Starts opening the downloads panel interface, anchored to the downloads
+   * button of the browser window.  The list of downloads to display is
+   * initialized the first time this method is called, and the panel is shown
+   * only when data is ready.
+   */
+  showPanel() {
+    DownloadsCommon.log("Opening the downloads panel.");
+
+    if (this.isPanelShowing) {
+      DownloadsCommon.log("Panel is already showing - focusing instead.");
+      this._focusPanel();
+      return;
+    }
+
+    this.initialize(() => {
+      let downloadsFooterButtons =
+        document.getElementById("downloadsFooterButtons");
+      if (DownloadsCommon.showPanelDropmarker) {
+        downloadsFooterButtons.classList.remove("downloadsHideDropmarker");
+      } else {
+        downloadsFooterButtons.classList.add("downloadsHideDropmarker");
+      }
+
+      // Delay displaying the panel because this function will sometimes be
+      // called while another window is closing (like the window for selecting
+      // whether to save or open the file), and that would cause the panel to
+      // close immediately.
+      setTimeout(() => this._openPopupIfDataReady(), 0);
+    });
+
+    DownloadsCommon.log("Waiting for the downloads panel to appear.");
+    this._state = this.kStateWaitingData;
+  },
+
+  /**
+   * Hides the downloads panel, if visible, but keeps the internal state so that
+   * the panel can be reopened quickly if required.
+   */
+  hidePanel() {
+    DownloadsCommon.log("Closing the downloads panel.");
+
+    if (!this.isPanelShowing) {
+      DownloadsCommon.log("Downloads panel is not showing - nothing to do.");
+      return;
+    }
+
+    this.panel.hidePopup();
+
+    // Ensure that we allow the panel to be reopened.  Note that, if the popup
+    // was open, then the onPopupHidden event handler has already updated the
+    // current state, otherwise we must update the state ourselves.
+    this._state = this.kStateHidden;
+    DownloadsCommon.log("Downloads panel is now closed.");
+  },
+
+  /**
+   * Indicates whether the panel is shown or will be shown.
+   */
+  get isPanelShowing() {
+    return this._state == this.kStateWaitingData ||
+           this._state == this.kStateWaitingAnchor ||
+           this._state == this.kStateShown;
+  },
+
+  /**
+   * Returns whether the user has started keyboard navigation.
+   */
+  get keyFocusing() {
+    return this.panel.hasAttribute("keyfocus");
+  },
+
+  /**
+   * Set to true if the user has started keyboard navigation, and we should be
+   * showing focusrings in the panel. Also adds a mousemove event handler to
+   * the panel which disables keyFocusing.
+   */
+  set keyFocusing(aValue) {
+    if (aValue) {
+      this.panel.setAttribute("keyfocus", "true");
+      this.panel.addEventListener("mousemove", this);
+    } else {
+      this.panel.removeAttribute("keyfocus");
+      this.panel.removeEventListener("mousemove", this);
+    }
+    return aValue;
+  },
+
+  /**
+   * Handles the mousemove event for the panel, which disables focusring
+   * visualization.
+   */
+  handleEvent(aEvent) {
+    switch (aEvent.type) {
+      case "mousemove":
+        this.keyFocusing = false;
+        break;
+      case "keydown":
+        return this._onKeyDown(aEvent);
+      case "keypress":
+        return this._onKeyPress(aEvent);
+      case "popupshown":
+        if (this.setHeightToFitOnShow) {
+          this.setHeightToFitOnShow = false;
+          this.setHeightToFit();
+        }
+        break;
+    }
+  },
+
+  setHeightToFit() {
+    if (this._state == this.kStateShown) {
+      DownloadsBlockedSubview.view.setHeightToFit();
+    } else {
+      this.setHeightToFitOnShow = true;
+    }
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Callback functions from DownloadsView
+
+  /**
+   * Called after data loading finished.
+   */
+  onViewLoadCompleted() {
+    this._openPopupIfDataReady();
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// User interface event functions
+
+  onWindowUnload() {
+    // This function is registered as an event listener, we can't use "this".
+    DownloadsPanel.terminate();
+  },
+
+  onPopupShown(aEvent) {
+    // Ignore events raised by nested popups.
+    if (aEvent.target != aEvent.currentTarget) {
+      return;
+    }
+
+    DownloadsCommon.log("Downloads panel has shown.");
+    this._state = this.kStateShown;
+
+    // Since at most one popup is open at any given time, we can set globally.
+    DownloadsCommon.getIndicatorData(window).attentionSuppressed = true;
+
+    // Ensure that the first item is selected when the panel is focused.
+    if (DownloadsView.richListBox.itemCount > 0 &&
+        DownloadsView.richListBox.selectedIndex == -1) {
+      DownloadsView.richListBox.selectedIndex = 0;
+    }
+
+    this._focusPanel();
+  },
+
+  onPopupHidden(aEvent) {
+    // Ignore events raised by nested popups.
+    if (aEvent.target != aEvent.currentTarget) {
+      return;
+    }
+
+    DownloadsCommon.log("Downloads panel has hidden.");
+
+    // Removes the keyfocus attribute so that we stop handling keyboard
+    // navigation.
+    this.keyFocusing = false;
+
+    // Since at most one popup is open at any given time, we can set globally.
+    DownloadsCommon.getIndicatorData(window).attentionSuppressed = false;
+
+    // Allow the anchor to be hidden.
+    DownloadsButton.releaseAnchor();
+
+    // Allow the panel to be reopened.
+    this._state = this.kStateHidden;
+  },
+
+  onFooterPopupShowing(aEvent) {
+    let itemClearList = document.getElementById("downloadsDropdownItemClearList");
+    if (DownloadsCommon.getData(window).canRemoveFinished) {
+      itemClearList.removeAttribute("hidden");
+    } else {
+      itemClearList.setAttribute("hidden", "true");
+    }
+    DownloadsViewController.updateCommands();
+
+    document.getElementById("downloadsFooter")
+      .setAttribute("showingdropdown", true);
+  },
+
+  onFooterPopupHidden(aEvent) {
+    document.getElementById("downloadsFooter")
+      .removeAttribute("showingdropdown");
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Related operations
+
+  /**
+   * Shows or focuses the user interface dedicated to downloads history.
+   */
+  showDownloadsHistory() {
+    DownloadsCommon.log("Showing download history.");
+    // Hide the panel before showing another window, otherwise focus will return
+    // to the browser window when the panel closes automatically.
+    this.hidePanel();
+
+    BrowserDownloadsUI();
+  },
+
+  openDownloadsFolder() {
+    Downloads.getPreferredDownloadsDirectory().then(downloadsPath => {
+      DownloadsCommon.showDirectory(new FileUtils.File(downloadsPath));
+    }).catch(Cu.reportError);
+    this.hidePanel();
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Internal functions
+
+  /**
+   * Attach event listeners to a panel element. These listeners should be
+   * removed in _unattachEventListeners. This is called automatically after the
+   * panel has successfully loaded.
+   */
+  _attachEventListeners() {
+    // Handle keydown to support accel-V.
+    this.panel.addEventListener("keydown", this, false);
+    // Handle keypress to be able to preventDefault() events before they reach
+    // the richlistbox, for keyboard navigation.
+    this.panel.addEventListener("keypress", this, false);
+    // Handle height adjustment on show.
+    this.panel.addEventListener("popupshown", this, false);
+  },
+
+  /**
+   * Unattach event listeners that were added in _attachEventListeners. This
+   * is called automatically on panel termination.
+   */
+  _unattachEventListeners() {
+    this.panel.removeEventListener("keydown", this, false);
+    this.panel.removeEventListener("keypress", this, false);
+    this.panel.removeEventListener("popupshown", this, false);
+  },
+
+  _onKeyPress(aEvent) {
+    // Handle unmodified keys only.
+    if (aEvent.altKey || aEvent.ctrlKey || aEvent.shiftKey || aEvent.metaKey) {
+      return;
+    }
+
+    let richListBox = DownloadsView.richListBox;
+
+    // If the user has pressed the tab, up, or down cursor key, start keyboard
+    // navigation, thus enabling focusrings in the panel.  Keyboard navigation
+    // is automatically disabled if the user moves the mouse on the panel, or
+    // if the panel is closed.
+    if ((aEvent.keyCode == Ci.nsIDOMKeyEvent.DOM_VK_TAB ||
+        aEvent.keyCode == Ci.nsIDOMKeyEvent.DOM_VK_UP ||
+        aEvent.keyCode == Ci.nsIDOMKeyEvent.DOM_VK_DOWN) &&
+        !this.keyFocusing) {
+      this.keyFocusing = true;
+      // Ensure there's a selection, we will show the focus ring around it and
+      // prevent the richlistbox from changing the selection.
+      if (DownloadsView.richListBox.selectedIndex == -1) {
+        DownloadsView.richListBox.selectedIndex = 0;
+      }
+      aEvent.preventDefault();
+      return;
+    }
+
+    if (aEvent.keyCode == Ci.nsIDOMKeyEvent.DOM_VK_DOWN) {
+      // If the last element in the list is selected, or the footer is already
+      // focused, focus the footer.
+      if (richListBox.selectedItem === richListBox.lastChild ||
+          document.activeElement.parentNode.id === "downloadsFooter") {
+        DownloadsFooter.focus();
+        aEvent.preventDefault();
+        return;
+      }
+    }
+
+    // Pass keypress events to the richlistbox view when it's focused.
+    if (document.activeElement === richListBox) {
+      DownloadsView.onDownloadKeyPress(aEvent);
+    }
+  },
+
+  /**
+   * Keydown listener that listens for the keys to start key focusing, as well
+   * as the the accel-V "paste" event, which initiates a file download if the
+   * pasted item can be resolved to a URI.
+   */
+  _onKeyDown(aEvent) {
+    // If the footer is focused and the downloads list has at least 1 element
+    // in it, focus the last element in the list when going up.
+    if (aEvent.keyCode == Ci.nsIDOMKeyEvent.DOM_VK_UP &&
+        document.activeElement.parentNode.id === "downloadsFooter" &&
+        DownloadsView.richListBox.firstChild) {
+      DownloadsView.richListBox.focus();
+      DownloadsView.richListBox.selectedItem = DownloadsView.richListBox.lastChild;
+      aEvent.preventDefault();
+      return;
+    }
+
+    let pasting = aEvent.keyCode == Ci.nsIDOMKeyEvent.DOM_VK_V &&
+                  aEvent.getModifierState("Accel");
+
+    if (!pasting) {
+      return;
+    }
+
+    DownloadsCommon.log("Received a paste event.");
+
+    let trans = Cc["@mozilla.org/widget/transferable;1"]
+                  .createInstance(Ci.nsITransferable);
+    trans.init(null);
+    let flavors = ["text/x-moz-url", "text/unicode"];
+    flavors.forEach(trans.addDataFlavor);
+    Services.clipboard.getData(trans, Services.clipboard.kGlobalClipboard);
+    // Getting the data or creating the nsIURI might fail
+    try {
+      let data = {};
+      trans.getAnyTransferData({}, data, {});
+      let [url, name] = data.value
+                            .QueryInterface(Ci.nsISupportsString)
+                            .data
+                            .split("\n");
+      if (!url) {
+        return;
+      }
+
+      let uri = NetUtil.newURI(url);
+      DownloadsCommon.log("Pasted URL seems valid. Starting download.");
+      DownloadURL(uri.spec, name, document);
+    } catch (ex) {}
+  },
+
+  /**
+   * Move focus to the main element in the downloads panel, unless another
+   * element in the panel is already focused.
+   */
+  _focusPanel() {
+    // We may be invoked while the panel is still waiting to be shown.
+    if (this._state != this.kStateShown) {
+      return;
+    }
+
+    let element = document.commandDispatcher.focusedElement;
+    while (element && element != this.panel) {
+      element = element.parentNode;
+    }
+    if (!element) {
+      if (DownloadsView.richListBox.itemCount > 0) {
+        DownloadsView.richListBox.focus();
+      } else {
+        DownloadsFooter.focus();
+      }
+    }
+  },
+
+  /**
+   * Opens the downloads panel when data is ready to be displayed.
+   */
+  _openPopupIfDataReady() {
+    // We don't want to open the popup if we already displayed it, or if we are
+    // still loading data.
+    if (this._state != this.kStateWaitingData || DownloadsView.loading) {
+      return;
+    }
+
+    this._state = this.kStateWaitingAnchor;
+
+    // Ensure the anchor is visible.  If that is not possible, show the panel
+    // anchored to the top area of the window, near the default anchor position.
+    DownloadsButton.getAnchor(anchor => {
+      // If somehow we've switched states already (by getting a panel hiding
+      // event before an overlay is loaded, for example), bail out.
+      if (this._state != this.kStateWaitingAnchor) {
+        return;
+      }
+
+      // At this point, if the window is minimized, opening the panel could fail
+      // without any notification, and there would be no way to either open or
+      // close the panel any more.  To prevent this, check if the window is
+      // minimized and in that case force the panel to the closed state.
+      if (window.windowState == Ci.nsIDOMChromeWindow.STATE_MINIMIZED) {
+        DownloadsButton.releaseAnchor();
+        this._state = this.kStateHidden;
+        return;
+      }
+
+      if (!anchor) {
+        DownloadsCommon.error("Downloads button cannot be found.");
+        return;
+      }
+
+      // When the panel is opened, we check if the target files of visible items
+      // still exist, and update the allowed items interactions accordingly.  We
+      // do these checks on a background thread, and don't prevent the panel to
+      // be displayed while these checks are being performed.
+      for (let viewItem of DownloadsView._visibleViewItems.values()) {
+        viewItem.download.refresh().catch(Cu.reportError);
+      }
+
+      DownloadsCommon.log("Opening downloads panel popup.");
+      this.panel.openPopup(anchor, "bottomcenter topright", 0, 0, false, null);
+    });
+  },
+};
+
+XPCOMUtils.defineConstant(this, "DownloadsPanel", DownloadsPanel);
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsOverlayLoader
+
+/**
+ * Allows loading the downloads panel and the status indicator interfaces on
+ * demand, to improve startup performance.
+ */
+const DownloadsOverlayLoader = {
+  /**
+   * We cannot load two overlays at the same time, thus we use a queue of
+   * pending load requests.
+   */
+  _loadRequests: [],
+
+  /**
+   * True while we are waiting for an overlay to be loaded.
+   */
+  _overlayLoading: false,
+
+  /**
+   * This object has a key for each overlay URI that is already loaded.
+   */
+  _loadedOverlays: {},
+
+  /**
+   * Loads the specified overlay and invokes the given callback when finished.
+   *
+   * @param aOverlay
+   *        String containing the URI of the overlay to load in the current
+   *        window.  If this overlay has already been loaded using this
+   *        function, then the overlay is not loaded again.
+   * @param aCallback
+   *        Invoked when loading is completed.  If the overlay is already
+   *        loaded, the function is called immediately.
+   */
+  ensureOverlayLoaded(aOverlay, aCallback) {
+    // The overlay is already loaded, invoke the callback immediately.
+    if (aOverlay in this._loadedOverlays) {
+      aCallback();
+      return;
+    }
+
+    // The callback will be invoked when loading is finished.
+    this._loadRequests.push({ overlay: aOverlay, callback: aCallback });
+    if (this._overlayLoading) {
+      return;
+    }
+
+    this._overlayLoading = true;
+    DownloadsCommon.log("Loading overlay ", aOverlay);
+    document.loadOverlay(aOverlay, () => {
+      this._overlayLoading = false;
+      this._loadedOverlays[aOverlay] = true;
+
+      this.processPendingRequests();
+    });
+  },
+
+  /**
+   * Re-processes all the currently pending requests, invoking the callbacks
+   * and/or loading more overlays as needed.  In most cases, there will be a
+   * single request for one overlay, that will be processed immediately.
+   */
+  processPendingRequests() {
+    // Re-process all the currently pending requests, yet allow more requests
+    // to be appended at the end of the array if we're not ready for them.
+    let currentLength = this._loadRequests.length;
+    for (let i = 0; i < currentLength; i++) {
+      let request = this._loadRequests.shift();
+
+      // We must call ensureOverlayLoaded again for each request, to check if
+      // the associated callback can be invoked now, or if we must still wait
+      // for the associated overlay to load.
+      this.ensureOverlayLoaded(request.overlay, request.callback);
+    }
+  },
+};
+
+XPCOMUtils.defineConstant(this, "DownloadsOverlayLoader", DownloadsOverlayLoader);
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsView
+
+/**
+ * Builds and updates the downloads list widget, responding to changes in the
+ * download state and real-time data.  In addition, handles part of the user
+ * interaction events raised by the downloads list widget.
+ */
+const DownloadsView = {
+  //////////////////////////////////////////////////////////////////////////////
+  //// Functions handling download items in the list
+
+  /**
+   * Maximum number of items shown by the list at any given time.
+   */
+  kItemCountLimit: 5,
+
+  /**
+   * Indicates whether there is an open contextMenu for a download item.
+   */
+  contextMenuOpen: false,
+
+  /**
+   * Indicates whether there is a DownloadsBlockedSubview open.
+   */
+  subViewOpen: false,
+
+  /**
+   * Indicates whether we are still loading downloads data asynchronously.
+   */
+  loading: false,
+
+  /**
+   * Ordered array of all Download objects.  We need to keep this array because
+   * only a limited number of items are shown at once, and if an item that is
+   * currently visible is removed from the list, we might need to take another
+   * item from the array and make it appear at the bottom.
+   */
+  _downloads: [],
+
+  /**
+   * Associates the visible Download objects with their corresponding
+   * DownloadsViewItem object.  There is a limited number of view items in the
+   * panel at any given time.
+   */
+  _visibleViewItems: new Map(),
+
+  /**
+   * Called when the number of items in the list changes.
+   */
+  _itemCountChanged() {
+    DownloadsCommon.log("The downloads item count has changed - we are tracking",
+                        this._downloads.length, "downloads in total.");
+    let count = this._downloads.length;
+    let hiddenCount = count - this.kItemCountLimit;
+
+    if (count > 0) {
+      DownloadsCommon.log("Setting the panel's hasdownloads attribute to true.");
+      DownloadsPanel.panel.setAttribute("hasdownloads", "true");
+    } else {
+      DownloadsCommon.log("Removing the panel's hasdownloads attribute.");
+      DownloadsPanel.panel.removeAttribute("hasdownloads");
+    }
+
+    // If we've got some hidden downloads, we should activate the
+    // DownloadsSummary. The DownloadsSummary will determine whether or not
+    // it's appropriate to actually display the summary.
+    DownloadsSummary.active = hiddenCount > 0;
+  },
+
+  /**
+   * Element corresponding to the list of downloads.
+   */
+  get richListBox() {
+    delete this.richListBox;
+    return this.richListBox = document.getElementById("downloadsListBox");
+  },
+
+  /**
+   * Element corresponding to the button for showing more downloads.
+   */
+  get downloadsHistory() {
+    delete this.downloadsHistory;
+    return this.downloadsHistory = document.getElementById("downloadsHistory");
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Callback functions from DownloadsData
+
+  /**
+   * Called before multiple downloads are about to be loaded.
+   */
+  onDataLoadStarting() {
+    DownloadsCommon.log("onDataLoadStarting called for DownloadsView.");
+    this.loading = true;
+  },
+
+  /**
+   * Called after data loading finished.
+   */
+  onDataLoadCompleted() {
+    DownloadsCommon.log("onDataLoadCompleted called for DownloadsView.");
+
+    this.loading = false;
+
+    // We suppressed item count change notifications during the batch load, at
+    // this point we should just call the function once.
+    this._itemCountChanged();
+
+    // Notify the panel that all the initially available downloads have been
+    // loaded.  This ensures that the interface is visible, if still required.
+    DownloadsPanel.onViewLoadCompleted();
+  },
+
+  /**
+   * Called when a new download data item is available, either during the
+   * asynchronous data load or when a new download is started.
+   *
+   * @param aDownload
+   *        Download object that was just added.
+   * @param aNewest
+   *        When true, indicates that this item is the most recent and should be
+   *        added in the topmost position.  This happens when a new download is
+   *        started.  When false, indicates that the item is the least recent
+   *        and should be appended.  The latter generally happens during the
+   *        asynchronous data load.
+   */
+  onDownloadAdded(download, aNewest) {
+    DownloadsCommon.log("A new download data item was added - aNewest =",
+                        aNewest);
+
+    if (aNewest) {
+      this._downloads.unshift(download);
+    } else {
+      this._downloads.push(download);
+    }
+
+    let itemsNowOverflow = this._downloads.length > this.kItemCountLimit;
+    if (aNewest || !itemsNowOverflow) {
+      // The newly added item is visible in the panel and we must add the
+      // corresponding element.  This is either because it is the first item, or
+      // because it was added at the bottom but the list still doesn't overflow.
+      this._addViewItem(download, aNewest);
+    }
+    if (aNewest && itemsNowOverflow) {
+      // If the list overflows, remove the last item from the panel to make room
+      // for the new one that we just added at the top.
+      this._removeViewItem(this._downloads[this.kItemCountLimit]);
+    }
+
+    // For better performance during batch loads, don't update the count for
+    // every item, because the interface won't be visible until load finishes.
+    if (!this.loading) {
+      this._itemCountChanged();
+    }
+  },
+
+  onDownloadStateChanged(download) {
+    let viewItem = this._visibleViewItems.get(download);
+    if (viewItem) {
+      viewItem.onStateChanged();
+    }
+  },
+
+  onDownloadChanged(download) {
+    let viewItem = this._visibleViewItems.get(download);
+    if (viewItem) {
+      viewItem.onChanged();
+    }
+  },
+
+  /**
+   * Called when a data item is removed.  Ensures that the widget associated
+   * with the view item is removed from the user interface.
+   *
+   * @param download
+   *        Download object that is being removed.
+   */
+  onDownloadRemoved(download) {
+    DownloadsCommon.log("A download data item was removed.");
+
+    let itemIndex = this._downloads.indexOf(download);
+    this._downloads.splice(itemIndex, 1);
+
+    if (itemIndex < this.kItemCountLimit) {
+      // The item to remove is visible in the panel.
+      this._removeViewItem(download);
+      if (this._downloads.length >= this.kItemCountLimit) {
+        // Reinsert the next item into the panel.
+        this._addViewItem(this._downloads[this.kItemCountLimit - 1], false);
+      }
+    }
+
+    this._itemCountChanged();
+
+    // Adjust the panel height if we removed items.
+    DownloadsPanel.setHeightToFit();
+  },
+
+  /**
+   * Associates each richlistitem for a download with its corresponding
+   * DownloadsViewItem object.
+   */
+  _itemsForElements: new Map(),
+
+  itemForElement(element) {
+    return this._itemsForElements.get(element);
+  },
+
+  /**
+   * Creates a new view item associated with the specified data item, and adds
+   * it to the top or the bottom of the list.
+   */
+  _addViewItem(download, aNewest)
+  {
+    DownloadsCommon.log("Adding a new DownloadsViewItem to the downloads list.",
+                        "aNewest =", aNewest);
+
+    let element = document.createElement("richlistitem");
+    let viewItem = new DownloadsViewItem(download, element);
+    this._visibleViewItems.set(download, viewItem);
+    this._itemsForElements.set(element, viewItem);
+    if (aNewest) {
+      this.richListBox.insertBefore(element, this.richListBox.firstChild);
+    } else {
+      this.richListBox.appendChild(element);
+    }
+  },
+
+  /**
+   * Removes the view item associated with the specified data item.
+   */
+  _removeViewItem(download) {
+    DownloadsCommon.log("Removing a DownloadsViewItem from the downloads list.");
+    let element = this._visibleViewItems.get(download).element;
+    let previousSelectedIndex = this.richListBox.selectedIndex;
+    this.richListBox.removeChild(element);
+    if (previousSelectedIndex != -1) {
+      this.richListBox.selectedIndex = Math.min(previousSelectedIndex,
+                                                this.richListBox.itemCount - 1);
+    }
+    this._visibleViewItems.delete(download);
+    this._itemsForElements.delete(element);
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// User interface event functions
+
+  /**
+   * Helper function to do commands on a specific download item.
+   *
+   * @param aEvent
+   *        Event object for the event being handled.  If the event target is
+   *        not a richlistitem that represents a download, this function will
+   *        walk up the parent nodes until it finds a DOM node that is.
+   * @param aCommand
+   *        The command to be performed.
+   */
+  onDownloadCommand(aEvent, aCommand) {
+    let target = aEvent.target;
+    while (target.nodeName != "richlistitem") {
+      target = target.parentNode;
+    }
+    DownloadsView.itemForElement(target).doCommand(aCommand);
+  },
+
+  onDownloadClick(aEvent) {
+    // Handle primary clicks only, and exclude the action button.
+    if (aEvent.button == 0 &&
+        !aEvent.originalTarget.hasAttribute("oncommand")) {
+      let target = aEvent.target;
+      while (target.nodeName != "richlistitem") {
+        target = target.parentNode;
+      }
+      let download = DownloadsView.itemForElement(target).download;
+      if (download.hasBlockedData) {
+        goDoCommand("downloadsCmd_showBlockedInfo");
+      } else {
+        goDoCommand("downloadsCmd_open");
+      }
+    }
+  },
+
+  /**
+   * Handles keypress events on a download item.
+   */
+  onDownloadKeyPress(aEvent) {
+    // Pressing the key on buttons should not invoke the action because the
+    // event has already been handled by the button itself.
+    if (aEvent.originalTarget.hasAttribute("command") ||
+        aEvent.originalTarget.hasAttribute("oncommand")) {
+      return;
+    }
+
+    if (aEvent.charCode == " ".charCodeAt(0)) {
+      goDoCommand("downloadsCmd_pauseResume");
+      return;
+    }
+
+    if (aEvent.keyCode == KeyEvent.DOM_VK_RETURN) {
+      goDoCommand("downloadsCmd_doDefault");
+    }
+  },
+
+  /**
+   * Event handlers to keep track of context menu state (open/closed) for
+   * download items.
+   */
+  onContextPopupShown(aEvent) {
+    // Ignore events raised by nested popups.
+    if (aEvent.target != aEvent.currentTarget) {
+      return;
+    }
+
+    DownloadsCommon.log("Context menu has shown.");
+    this.contextMenuOpen = true;
+  },
+
+  onContextPopupHidden(aEvent) {
+    // Ignore events raised by nested popups.
+    if (aEvent.target != aEvent.currentTarget) {
+      return;
+    }
+
+    DownloadsCommon.log("Context menu has hidden.");
+    this.contextMenuOpen = false;
+  },
+
+  /**
+   * Mouse listeners to handle selection on hover.
+   */
+  onDownloadMouseOver(aEvent) {
+    if (!(this.contextMenuOpen || this.subViewOpen) &&
+        aEvent.target.parentNode == this.richListBox) {
+      this.richListBox.selectedItem = aEvent.target;
+    }
+  },
+
+  onDownloadMouseOut(aEvent) {
+    if (!(this.contextMenuOpen || this.subViewOpen) &&
+        aEvent.target.parentNode == this.richListBox) {
+      // If the destination element is outside of the richlistitem, clear the
+      // selection.
+      let element = aEvent.relatedTarget;
+      while (element && element != aEvent.target) {
+        element = element.parentNode;
+      }
+      if (!element) {
+        this.richListBox.selectedIndex = -1;
+      }
+    }
+  },
+
+  onDownloadContextMenu(aEvent) {
+    let element = this.richListBox.selectedItem;
+    if (!element) {
+      return;
+    }
+
+    DownloadsViewController.updateCommands();
+
+    // Set the state attribute so that only the appropriate items are displayed.
+    let contextMenu = document.getElementById("downloadsContextMenu");
+    contextMenu.setAttribute("state", element.getAttribute("state"));
+    contextMenu.classList.toggle("temporary-block",
+                                 element.classList.contains("temporary-block"));
+  },
+
+  onDownloadDragStart(aEvent) {
+    let element = this.richListBox.selectedItem;
+    if (!element) {
+      return;
+    }
+
+    // We must check for existence synchronously because this is a DOM event.
+    let file = new FileUtils.File(DownloadsView.itemForElement(element)
+                                               .download.target.path);
+    if (!file.exists()) {
+      return;
+    }
+
+    let dataTransfer = aEvent.dataTransfer;
+    dataTransfer.mozSetDataAt("application/x-moz-file", file, 0);
+    dataTransfer.effectAllowed = "copyMove";
+    let spec = NetUtil.newURI(file).spec;
+    dataTransfer.setData("text/uri-list", spec);
+    dataTransfer.setData("text/plain", spec);
+    dataTransfer.addElement(element);
+
+    aEvent.stopPropagation();
+  },
+}
+
+XPCOMUtils.defineConstant(this, "DownloadsView", DownloadsView);
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsViewItem
+
+/**
+ * Builds and updates a single item in the downloads list widget, responding to
+ * changes in the download state and real-time data, and handles the user
+ * interaction events related to a single item in the downloads list widgets.
+ *
+ * @param download
+ *        Download object to be associated with the view item.
+ * @param aElement
+ *        XUL element corresponding to the single download item in the view.
+ */
+function DownloadsViewItem(download, aElement) {
+  this.download = download;
+  this.element = aElement;
+  this.element._shell = this;
+
+  this.element.setAttribute("type", "download");
+  this.element.classList.add("download-state");
+
+  this._updateState();
+}
+
+DownloadsViewItem.prototype = {
+  __proto__: DownloadsViewUI.DownloadElementShell.prototype,
+
+  /**
+   * The XUL element corresponding to the associated richlistbox item.
+   */
+  _element: null,
+
+  onStateChanged() {
+    this._updateState();
+  },
+
+  onChanged() {
+    this._updateProgress();
+  },
+
+  isCommandEnabled(aCommand) {
+    switch (aCommand) {
+      case "downloadsCmd_open": {
+        if (!this.download.succeeded) {
+          return false;
+        }
+
+        let file = new FileUtils.File(this.download.target.path);
+        return file.exists();
+      }
+      case "downloadsCmd_show": {
+        let file = new FileUtils.File(this.download.target.path);
+        if (file.exists()) {
+          return true;
+        }
+
+        if (!this.download.target.partFilePath) {
+          return false;
+        }
+
+        let partFile = new FileUtils.File(this.download.target.partFilePath);
+        return partFile.exists();
+      }
+      case "cmd_delete":
+      case "downloadsCmd_cancel":
+      case "downloadsCmd_copyLocation":
+      case "downloadsCmd_doDefault":
+        return true;
+      case "downloadsCmd_showBlockedInfo":
+        return this.download.hasBlockedData;
+    }
+    return DownloadsViewUI.DownloadElementShell.prototype
+                          .isCommandEnabled.call(this, aCommand);
+  },
+
+  doCommand(aCommand) {
+    if (this.isCommandEnabled(aCommand)) {
+      this[aCommand]();
+    }
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Item commands
+
+  cmd_delete() {
+    DownloadsCommon.removeAndFinalizeDownload(this.download);
+    PlacesUtils.bhistory.removePage(
+                           NetUtil.newURI(this.download.source.url));
+  },
+
+  downloadsCmd_unblock() {
+    DownloadsPanel.hidePanel();
+    this.confirmUnblock(window, "unblock");
+  },
+
+  downloadsCmd_chooseUnblock() {
+    DownloadsPanel.hidePanel();
+    this.confirmUnblock(window, "chooseUnblock");
+  },
+
+  downloadsCmd_unblockAndOpen() {
+    DownloadsPanel.hidePanel();
+    this.unblockAndOpenDownload().catch(Cu.reportError);
+  },
+
+  downloadsCmd_open() {
+    this.download.launch().catch(Cu.reportError);
+
+    // We explicitly close the panel here to give the user the feedback that
+    // their click has been received, and we're handling the action.
+    // Otherwise, we'd have to wait for the file-type handler to execute
+    // before the panel would close. This also helps to prevent the user from
+    // accidentally opening a file several times.
+    DownloadsPanel.hidePanel();
+  },
+
+  downloadsCmd_show() {
+    let file = new FileUtils.File(this.download.target.path);
+    DownloadsCommon.showDownloadedFile(file);
+
+    // We explicitly close the panel here to give the user the feedback that
+    // their click has been received, and we're handling the action.
+    // Otherwise, we'd have to wait for the operating system file manager
+    // window to open before the panel closed. This also helps to prevent the
+    // user from opening the containing folder several times.
+    DownloadsPanel.hidePanel();
+  },
+
+  downloadsCmd_showBlockedInfo() {
+    DownloadsBlockedSubview.toggle(this.element,
+                                   ...this.rawBlockedTitleAndDetails);
+  },
+
+  downloadsCmd_openReferrer() {
+    openURL(this.download.source.referrer);
+  },
+
+  downloadsCmd_copyLocation() {
+    let clipboard = Cc["@mozilla.org/widget/clipboardhelper;1"]
+                    .getService(Ci.nsIClipboardHelper);
+    clipboard.copyString(this.download.source.url);
+  },
+
+  downloadsCmd_doDefault() {
+    let defaultCommand = this.currentDefaultCommandName;
+    if (defaultCommand && this.isCommandEnabled(defaultCommand)) {
+      this.doCommand(defaultCommand);
+    }
+  },
+};
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsViewController
+
+/**
+ * Handles part of the user interaction events raised by the downloads list
+ * widget, in particular the "commands" that apply to multiple items, and
+ * dispatches the commands that apply to individual items.
+ */
+const DownloadsViewController = {
+  //////////////////////////////////////////////////////////////////////////////
+  //// Initialization and termination
+
+  initialize() {
+    window.controllers.insertControllerAt(0, this);
+  },
+
+  terminate() {
+    window.controllers.removeController(this);
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// nsIController
+
+  supportsCommand(aCommand) {
+    if (aCommand === "downloadsCmd_clearList") {
+      return true;
+    }
+    // Firstly, determine if this is a command that we can handle.
+    if (!DownloadsViewUI.isCommandName(aCommand)) {
+      return false;
+    }
+    if (!(aCommand in this) &&
+        !(aCommand in DownloadsViewItem.prototype)) {
+      return false;
+    }
+    // The currently supported commands depend on whether the blocked subview is
+    // showing.  If it is, then take the following path.
+    if (DownloadsBlockedSubview.view.showingSubView) {
+      let blockedSubviewCmds = [
+        "downloadsCmd_unblockAndOpen",
+        "cmd_delete",
+      ];
+      return blockedSubviewCmds.indexOf(aCommand) >= 0;
+    }
+    // If the blocked subview is not showing, then determine if focus is on a
+    // control in the downloads list.
+    let element = document.commandDispatcher.focusedElement;
+    while (element && element != DownloadsView.richListBox) {
+      element = element.parentNode;
+    }
+    // We should handle the command only if the downloads list is among the
+    // ancestors of the focused element.
+    return !!element;
+  },
+
+  isCommandEnabled(aCommand) {
+    // Handle commands that are not selection-specific.
+    if (aCommand == "downloadsCmd_clearList") {
+      return DownloadsCommon.getData(window).canRemoveFinished;
+    }
+
+    // Other commands are selection-specific.
+    let element = DownloadsView.richListBox.selectedItem;
+    return element && DownloadsView.itemForElement(element)
+                                   .isCommandEnabled(aCommand);
+  },
+
+  doCommand(aCommand) {
+    // If this command is not selection-specific, execute it.
+    if (aCommand in this) {
+      this[aCommand]();
+      return;
+    }
+
+    // Other commands are selection-specific.
+    let element = DownloadsView.richListBox.selectedItem;
+    if (element) {
+      // The doCommand function also checks if the command is enabled.
+      DownloadsView.itemForElement(element).doCommand(aCommand);
+    }
+  },
+
+  onEvent() {},
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Other functions
+
+  updateCommands() {
+    function updateCommandsForObject(object) {
+      for (let name in object) {
+        if (DownloadsViewUI.isCommandName(name)) {
+          goUpdateCommand(name);
+        }
+      }
+    }
+    updateCommandsForObject(this);
+    updateCommandsForObject(DownloadsViewItem.prototype);
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Selection-independent commands
+
+  downloadsCmd_clearList() {
+    DownloadsCommon.getData(window).removeFinished();
+  },
+};
+
+XPCOMUtils.defineConstant(this, "DownloadsViewController", DownloadsViewController);
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsSummary
+
+/**
+ * Manages the summary at the bottom of the downloads panel list if the number
+ * of items in the list exceeds the panels limit.
+ */
+const DownloadsSummary = {
+
+  /**
+   * Sets the active state of the summary. When active, the summary subscribes
+   * to the DownloadsCommon DownloadsSummaryData singleton.
+   *
+   * @param aActive
+   *        Set to true to activate the summary.
+   */
+  set active(aActive) {
+    if (aActive == this._active || !this._summaryNode) {
+      return this._active;
+    }
+    if (aActive) {
+      DownloadsCommon.getSummary(window, DownloadsView.kItemCountLimit)
+                     .refreshView(this);
+    } else {
+      DownloadsFooter.showingSummary = false;
+    }
+
+    return this._active = aActive;
+  },
+
+  /**
+   * Returns the active state of the downloads summary.
+   */
+  get active() {
+    return this._active;
+  },
+
+  _active: false,
+
+  /**
+   * Sets whether or not we show the progress bar.
+   *
+   * @param aShowingProgress
+   *        True if we should show the progress bar.
+   */
+  set showingProgress(aShowingProgress) {
+    if (aShowingProgress) {
+      this._summaryNode.setAttribute("inprogress", "true");
+    } else {
+      this._summaryNode.removeAttribute("inprogress");
+    }
+    // If progress isn't being shown, then we simply do not show the summary.
+    return DownloadsFooter.showingSummary = aShowingProgress;
+  },
+
+  /**
+   * Sets the amount of progress that is visible in the progress bar.
+   *
+   * @param aValue
+   *        A value between 0 and 100 to represent the progress of the
+   *        summarized downloads.
+   */
+  set percentComplete(aValue) {
+    if (this._progressNode) {
+      this._progressNode.setAttribute("value", aValue);
+    }
+    return aValue;
+  },
+
+  /**
+   * Sets the description for the download summary.
+   *
+   * @param aValue
+   *        A string representing the description of the summarized
+   *        downloads.
+   */
+  set description(aValue) {
+    if (this._descriptionNode) {
+      this._descriptionNode.setAttribute("value", aValue);
+      this._descriptionNode.setAttribute("tooltiptext", aValue);
+    }
+    return aValue;
+  },
+
+  /**
+   * Sets the details for the download summary, such as the time remaining,
+   * the amount of bytes transferred, etc.
+   *
+   * @param aValue
+   *        A string representing the details of the summarized
+   *        downloads.
+   */
+  set details(aValue) {
+    if (this._detailsNode) {
+      this._detailsNode.setAttribute("value", aValue);
+      this._detailsNode.setAttribute("tooltiptext", aValue);
+    }
+    return aValue;
+  },
+
+  /**
+   * Focuses the root element of the summary.
+   */
+  focus() {
+    if (this._summaryNode) {
+      this._summaryNode.focus();
+    }
+  },
+
+  /**
+   * Respond to keydown events on the Downloads Summary node.
+   *
+   * @param aEvent
+   *        The keydown event being handled.
+   */
+  onKeyDown(aEvent) {
+    if (aEvent.charCode == " ".charCodeAt(0) ||
+        aEvent.keyCode == KeyEvent.DOM_VK_RETURN) {
+      DownloadsPanel.showDownloadsHistory();
+    }
+  },
+
+  /**
+   * Respond to click events on the Downloads Summary node.
+   *
+   * @param aEvent
+   *        The click event being handled.
+   */
+  onClick(aEvent) {
+    DownloadsPanel.showDownloadsHistory();
+  },
+
+  /**
+   * Element corresponding to the root of the downloads summary.
+   */
+  get _summaryNode() {
+    let node = document.getElementById("downloadsSummary");
+    if (!node) {
+      return null;
+    }
+    delete this._summaryNode;
+    return this._summaryNode = node;
+  },
+
+  /**
+   * Element corresponding to the progress bar in the downloads summary.
+   */
+  get _progressNode() {
+    let node = document.getElementById("downloadsSummaryProgress");
+    if (!node) {
+      return null;
+    }
+    delete this._progressNode;
+    return this._progressNode = node;
+  },
+
+  /**
+   * Element corresponding to the main description of the downloads
+   * summary.
+   */
+  get _descriptionNode() {
+    let node = document.getElementById("downloadsSummaryDescription");
+    if (!node) {
+      return null;
+    }
+    delete this._descriptionNode;
+    return this._descriptionNode = node;
+  },
+
+  /**
+   * Element corresponding to the secondary description of the downloads
+   * summary.
+   */
+  get _detailsNode() {
+    let node = document.getElementById("downloadsSummaryDetails");
+    if (!node) {
+      return null;
+    }
+    delete this._detailsNode;
+    return this._detailsNode = node;
+  }
+};
+
+XPCOMUtils.defineConstant(this, "DownloadsSummary", DownloadsSummary);
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsFooter
+
+/**
+ * Manages events sent to to the footer vbox, which contains both the
+ * DownloadsSummary as well as the "Show All Downloads" button.
+ */
+const DownloadsFooter = {
+
+  /**
+   * Focuses the appropriate element within the footer. If the summary
+   * is visible, focus it. If not, focus the "Show All Downloads"
+   * button.
+   */
+  focus() {
+    if (this._showingSummary) {
+      DownloadsSummary.focus();
+    } else {
+      DownloadsView.downloadsHistory.focus();
+    }
+  },
+
+  _showingSummary: false,
+
+  /**
+   * Sets whether or not the Downloads Summary should be displayed in the
+   * footer. If not, the "Show All Downloads" button is shown instead.
+   */
+  set showingSummary(aValue) {
+    if (this._footerNode) {
+      if (aValue) {
+        this._footerNode.setAttribute("showingsummary", "true");
+      } else {
+        this._footerNode.removeAttribute("showingsummary");
+      }
+      if (!aValue && this._showingSummary) {
+        // Make sure the panel's height shrinks when the summary is hidden.
+        DownloadsPanel.setHeightToFit();
+      }
+      this._showingSummary = aValue;
+    }
+    return aValue;
+  },
+
+  /**
+   * Element corresponding to the footer of the downloads panel.
+   */
+  get _footerNode() {
+    let node = document.getElementById("downloadsFooter");
+    if (!node) {
+      return null;
+    }
+    delete this._footerNode;
+    return this._footerNode = node;
+  }
+};
+
+XPCOMUtils.defineConstant(this, "DownloadsFooter", DownloadsFooter);
+
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsBlockedSubview
+
+/**
+ * Manages the blocked subview that slides in when you click a blocked download.
+ */
+const DownloadsBlockedSubview = {
+
+  get subview() {
+    let subview = document.getElementById("downloadsPanel-blockedSubview");
+    delete this.subview;
+    return this.subview = subview;
+  },
+
+  /**
+   * Elements in the subview.
+   */
+  get elements() {
+    let idSuffixes = [
+      "title",
+      "details1",
+      "details2",
+      "openButton",
+      "deleteButton",
+    ];
+    let elements = idSuffixes.reduce((memo, s) => {
+      memo[s] = document.getElementById("downloadsPanel-blockedSubview-" + s);
+      return memo;
+    }, {});
+    delete this.elements;
+    return this.elements = elements;
+  },
+
+  /**
+   * The multiview that contains both the main view and the subview.
+   */
+  get view() {
+    let view = document.getElementById("downloadsPanel-multiView");
+    delete this.view;
+    return this.view = view;
+  },
+
+  /**
+   * The blocked-download richlistitem element that was clicked to show the
+   * subview.  If the subview is not showing, this is undefined.
+   */
+  element: undefined,
+
+  /**
+   * Slides in the blocked subview.
+   *
+   * @param element
+   *        The blocked-download richlistitem element that was clicked.
+   * @param title
+   *        The title to show in the subview.
+   * @param details
+   *        An array of strings with information about the block.
+   */
+  toggle(element, title, details) {
+    if (this.view.showingSubView) {
+      this.hide();
+      return;
+    }
+
+    this.element = element;
+    element.setAttribute("showingsubview", "true");
+    DownloadsView.subViewOpen = true;
+    DownloadsViewController.updateCommands();
+
+    let e = this.elements;
+    let s = DownloadsCommon.strings;
+    e.title.textContent = title;
+    e.details1.textContent = details[0];
+    e.details2.textContent = details[1];
+    e.openButton.label = s.unblockButtonOpen;
+    e.deleteButton.label = s.unblockButtonConfirmBlock;
+
+    let verdict = element.getAttribute("verdict");
+    this.subview.setAttribute("verdict", verdict);
+    this.subview.addEventListener("ViewHiding", this);
+
+    this.view.showSubView(this.subview.id);
+
+    // Without this, the mainView is more narrow than the panel once all
+    // downloads are removed from the panel.
+    document.getElementById("downloadsPanel-mainView").style.minWidth =
+      window.getComputedStyle(this.view).width;
+  },
+
+  handleEvent(event) {
+    switch (event.type) {
+      case "ViewHiding":
+        this.subview.removeEventListener(event.type, this);
+        this.element.removeAttribute("showingsubview");
+        DownloadsView.subViewOpen = false;
+        delete this.element;
+        break;
+      default:
+        DownloadsCommon.log("Unhandled DownloadsBlockedSubview event: " +
+                            event.type);
+        break;
+    }
+  },
+
+  /**
+   * Slides out the blocked subview and shows the main view.
+   */
+  hide() {
+    this.view.showMainView();
+    // The point of this is to focus the proper element in the panel now that
+    // the main view is showing again.  showPanel handles that.
+    DownloadsPanel.showPanel();
+  },
+
+  /**
+   * Deletes the download and hides the entire panel.
+   */
+  confirmBlock() {
+    goDoCommand("cmd_delete");
+    DownloadsPanel.hidePanel();
+  },
+};
+
+XPCOMUtils.defineConstant(this, "DownloadsBlockedSubview",
+                          DownloadsBlockedSubview);
diff --git a/browser/components/downloads/content/downloadsOverlay.xul b/browser/components/downloads/content/downloadsOverlay.xul
new file mode 100644
index 000000000..9fe2ee022
--- /dev/null
+++ b/browser/components/downloads/content/downloadsOverlay.xul
@@ -0,0 +1,210 @@
+<?xml version="1.0"?>
+# -*- Mode: HTML; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+# vim: set ts=2 et sw=2 tw=80:
+# 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/.
+
+<?xml-stylesheet href="chrome://browser/content/downloads/downloads.css"?>
+<?xml-stylesheet href="chrome://browser/skin/downloads/downloads.css"?>
+
+<!DOCTYPE overlay SYSTEM "chrome://browser/locale/downloads/downloads.dtd">
+
+<overlay xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+         id="downloadsOverlay">
+
+  <commandset>
+    <command id="downloadsCmd_doDefault"
+             oncommand="goDoCommand('downloadsCmd_doDefault')"/>
+    <command id="downloadsCmd_pauseResume"
+             oncommand="goDoCommand('downloadsCmd_pauseResume')"/>
+    <command id="downloadsCmd_cancel"
+             oncommand="goDoCommand('downloadsCmd_cancel')"/>
+    <command id="downloadsCmd_unblock"
+             oncommand="goDoCommand('downloadsCmd_unblock')"/>
+    <command id="downloadsCmd_chooseUnblock"
+             oncommand="goDoCommand('downloadsCmd_chooseUnblock')"/>
+    <command id="downloadsCmd_unblockAndOpen"
+             oncommand="goDoCommand('downloadsCmd_unblockAndOpen')"/>
+    <command id="downloadsCmd_confirmBlock"
+             oncommand="goDoCommand('downloadsCmd_confirmBlock')"/>
+    <command id="downloadsCmd_open"
+             oncommand="goDoCommand('downloadsCmd_open')"/>
+    <command id="downloadsCmd_show"
+             oncommand="goDoCommand('downloadsCmd_show')"/>
+    <command id="downloadsCmd_retry"
+             oncommand="goDoCommand('downloadsCmd_retry')"/>
+    <command id="downloadsCmd_openReferrer"
+             oncommand="goDoCommand('downloadsCmd_openReferrer')"/>
+    <command id="downloadsCmd_copyLocation"
+             oncommand="goDoCommand('downloadsCmd_copyLocation')"/>
+    <command id="downloadsCmd_clearList"
+             oncommand="goDoCommand('downloadsCmd_clearList')"/>
+  </commandset>
+
+  <popupset id="mainPopupSet">
+    <!-- The panel has level="top" to ensure that it is never hidden by the
+         taskbar on Windows.  See bug 672365.  For accessibility to screen
+         readers, we use a label on the panel instead of the anchor because the
+         panel can also be displayed without an anchor. -->
+    <panel id="downloadsPanel"
+           aria-label="&downloads.title;"
+           role="group"
+           type="arrow"
+           orient="vertical"
+           level="top"
+           onpopupshown="DownloadsPanel.onPopupShown(event);"
+           onpopuphidden="DownloadsPanel.onPopupHidden(event);">
+      <!-- The following popup menu should be a child of the panel element,
+           otherwise flickering may occur when the cursor is moved over the area
+           of a disabled menu item that overlaps the panel.  See bug 492960. -->
+      <menupopup id="downloadsContextMenu"
+                 onpopupshown="DownloadsView.onContextPopupShown(event);"
+                 onpopuphidden="DownloadsView.onContextPopupHidden(event);"
+                 class="download-state">
+        <menuitem command="downloadsCmd_pauseResume"
+                  class="downloadPauseMenuItem"
+                  label="&cmd.pause.label;"
+                  accesskey="&cmd.pause.accesskey;"/>
+        <menuitem command="downloadsCmd_pauseResume"
+                  class="downloadResumeMenuItem"
+                  label="&cmd.resume.label;"
+                  accesskey="&cmd.resume.accesskey;"/>
+        <menuitem command="downloadsCmd_cancel"
+                  class="downloadCancelMenuItem"
+                  label="&cmd.cancel.label;"
+                  accesskey="&cmd.cancel.accesskey;"/>
+        <menuitem command="downloadsCmd_unblock"
+                  class="downloadUnblockMenuItem"
+                  label="&cmd.unblock2.label;"
+                  accesskey="&cmd.unblock2.accesskey;"/>
+        <menuitem command="cmd_delete"
+                  class="downloadRemoveFromHistoryMenuItem"
+                  label="&cmd.removeFromHistory.label;"
+                  accesskey="&cmd.removeFromHistory.accesskey;"/>
+        <menuitem command="downloadsCmd_show"
+                  class="downloadShowMenuItem"
+#ifdef XP_MACOSX
+                  label="&cmd.showMac.label;"
+                  accesskey="&cmd.showMac.accesskey;"
+#else
+                  label="&cmd.show.label;"
+                  accesskey="&cmd.show.accesskey;"
+#endif
+                  />
+
+        <menuseparator class="downloadCommandsSeparator"/>
+
+        <menuitem command="downloadsCmd_openReferrer"
+                  label="&cmd.goToDownloadPage.label;"
+                  accesskey="&cmd.goToDownloadPage.accesskey;"/>
+        <menuitem command="downloadsCmd_copyLocation"
+                  label="&cmd.copyDownloadLink.label;"
+                  accesskey="&cmd.copyDownloadLink.accesskey;"/>
+
+        <menuseparator/>
+
+        <menuitem command="downloadsCmd_clearList"
+                  label="&cmd.clearList2.label;"
+                  accesskey="&cmd.clearList2.accesskey;"/>
+      </menupopup>
+
+      <panelmultiview id="downloadsPanel-multiView"
+                      mainViewId="downloadsPanel-mainView"
+                      align="stretch">
+
+        <panelview id="downloadsPanel-mainView"
+                   flex="1"
+                   align="stretch">
+          <richlistbox id="downloadsListBox"
+                       context="downloadsContextMenu"
+                       onmouseover="DownloadsView.onDownloadMouseOver(event);"
+                       onmouseout="DownloadsView.onDownloadMouseOut(event);"
+                       oncontextmenu="DownloadsView.onDownloadContextMenu(event);"
+                       ondragstart="DownloadsView.onDownloadDragStart(event);"/>
+          <description id="emptyDownloads"
+                       mousethrough="always">
+             &downloadsPanelEmpty.label;
+          </description>
+          <spacer flex="1"/>
+          <vbox id="downloadsFooter"
+                class="downloadsPanelFooter">
+            <stack>
+              <hbox id="downloadsSummary"
+                    align="center"
+                    orient="horizontal"
+                    onkeydown="DownloadsSummary.onKeyDown(event);"
+                    onclick="DownloadsSummary.onClick(event);">
+                <image class="downloadTypeIcon" />
+                <vbox pack="center"
+                      class="downloadContainer"
+                      style="width: &downloadDetails.width;">
+                  <description id="downloadsSummaryDescription"
+                               style="min-width: &downloadsSummary.minWidth2;"/>
+                  <progressmeter id="downloadsSummaryProgress"
+                                 class="downloadProgress"
+                                 min="0"
+                                 max="100"
+                                 mode="normal" />
+                  <description id="downloadsSummaryDetails"
+                               crop="end"/>
+                </vbox>
+              </hbox>
+              <hbox id="downloadsFooterButtons">
+                <button id="downloadsHistory"
+                        class="downloadsPanelFooterButton"
+                        label="&downloadsHistory.label;"
+                        accesskey="&downloadsHistory.accesskey;"
+                        flex="1"
+                        oncommand="DownloadsPanel.showDownloadsHistory();"/>
+                <toolbarseparator id="downloadsFooterButtonsSplitter"
+                        class="downloadsDropmarkerSplitter"/>
+                <button id="downloadsFooterDropmarker"
+                        class="downloadsPanelFooterButton downloadsDropmarker"
+                        type="menu">
+                  <menupopup id="downloadSubPanel"
+                             onpopupshowing="DownloadsPanel.onFooterPopupShowing(event);"
+                             onpopuphidden="DownloadsPanel.onFooterPopupHidden(event);"
+                             position="after_end">
+                    <menuitem id="downloadsDropdownItemClearList"
+                              command="downloadsCmd_clearList"
+                              label="&cmd.clearList2.label;"/>
+                    <menuitem id="downloadsDropdownItemOpenDownloadsFolder"
+                              oncommand="DownloadsPanel.openDownloadsFolder();"
+                              label="&openDownloadsFolder.label;"/>
+                  </menupopup>
+                </button>
+              </hbox>
+            </stack>
+          </vbox>
+        </panelview>
+
+        <panelview id="downloadsPanel-blockedSubview"
+                   orient="vertical"
+                   flex="1">
+          <description id="downloadsPanel-blockedSubview-title"/>
+          <description id="downloadsPanel-blockedSubview-details1"/>
+          <description id="downloadsPanel-blockedSubview-details2"/>
+          <spacer flex="1"/>
+          <hbox id="downloadsPanel-blockedSubview-buttons"
+                class="downloadsPanelFooter"
+                align="stretch">
+            <button id="downloadsPanel-blockedSubview-openButton"
+                    class="downloadsPanelFooterButton"
+                    command="downloadsCmd_unblockAndOpen"
+                    flex="1"/>
+            <toolbarseparator/>
+            <button id="downloadsPanel-blockedSubview-deleteButton"
+                    class="downloadsPanelFooterButton"
+                    oncommand="DownloadsBlockedSubview.confirmBlock();"
+                    default="true"
+                    flex="1"/>
+          </hbox>
+        </panelview>
+
+      </panelmultiview>
+
+    </panel>
+  </popupset>
+</overlay>
diff --git a/browser/components/downloads/content/indicator.js b/browser/components/downloads/content/indicator.js
new file mode 100644
index 000000000..4c22a6e5d
--- /dev/null
+++ b/browser/components/downloads/content/indicator.js
@@ -0,0 +1,606 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/**
+ * Handles the indicator that displays the progress of ongoing downloads, which
+ * is also used as the anchor for the downloads panel.
+ *
+ * This module includes the following constructors and global objects:
+ *
+ * DownloadsButton
+ * Main entry point for the downloads indicator.  Depending on how the toolbars
+ * have been customized, this object determines if we should show a fully
+ * functional indicator, a placeholder used during customization and in the
+ * customization palette, or a neutral view as a temporary anchor for the
+ * downloads panel.
+ *
+ * DownloadsIndicatorView
+ * Builds and updates the actual downloads status widget, responding to changes
+ * in the global status data, or provides a neutral view if the indicator is
+ * removed from the toolbars and only used as a temporary anchor.  In addition,
+ * handles the user interaction events raised by the widget.
+ */
+
+"use strict";
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsButton
+
+/**
+ * Main entry point for the downloads indicator.  Depending on how the toolbars
+ * have been customized, this object determines if we should show a fully
+ * functional indicator, a placeholder used during customization and in the
+ * customization palette, or a neutral view as a temporary anchor for the
+ * downloads panel.
+ */
+const DownloadsButton = {
+  /**
+   * Location of the indicator overlay.
+   */
+  get kIndicatorOverlay() {
+    return "chrome://browser/content/downloads/indicatorOverlay.xul";
+  },
+
+  /**
+   * Returns a reference to the downloads button position placeholder, or null
+   * if not available because it has been removed from the toolbars.
+   */
+  get _placeholder() {
+    return document.getElementById("downloads-button");
+  },
+
+  /**
+   * This function is called asynchronously just after window initialization.
+   *
+   * NOTE: This function should limit the input/output it performs to improve
+   *       startup time.
+   */
+  initializeIndicator() {
+    DownloadsIndicatorView.ensureInitialized();
+  },
+
+  /**
+   * Indicates whether toolbar customization is in progress.
+   */
+  _customizing: false,
+
+  /**
+   * This function is called when toolbar customization starts.
+   *
+   * During customization, we never show the actual download progress indication
+   * or the event notifications, but we show a neutral placeholder.  The neutral
+   * placeholder is an ordinary button defined in the browser window that can be
+   * moved freely between the toolbars and the customization palette.
+   */
+  customizeStart() {
+    // Prevent the indicator from being displayed as a temporary anchor
+    // during customization, even if requested using the getAnchor method.
+    this._customizing = true;
+    this._anchorRequested = false;
+  },
+
+  /**
+   * This function is called when toolbar customization ends.
+   */
+  customizeDone() {
+    this._customizing = false;
+    DownloadsIndicatorView.afterCustomize();
+  },
+
+  /**
+   * Determines the position where the indicator should appear, and moves its
+   * associated element to the new position.
+   *
+   * @return Anchor element, or null if the indicator is not visible.
+   */
+  _getAnchorInternal() {
+    let indicator = DownloadsIndicatorView.indicator;
+    if (!indicator) {
+      // Exit now if the indicator overlay isn't loaded yet, or if the button
+      // is not in the document.
+      return null;
+    }
+
+    indicator.open = this._anchorRequested;
+
+    let widget = CustomizableUI.getWidget("downloads-button")
+                               .forWindow(window);
+     // Determine if the indicator is located on an invisible toolbar.
+     if (!isElementVisible(indicator.parentNode) && !widget.overflowed) {
+       return null;
+     }
+
+    return DownloadsIndicatorView.indicatorAnchor;
+  },
+
+  /**
+   * Checks whether the indicator is, or will soon be visible in the browser
+   * window.
+   *
+   * @param aCallback
+   *        Called once the indicator overlay has loaded. Gets a boolean
+   *        argument representing the indicator visibility.
+   */
+  checkIsVisible(aCallback) {
+    DownloadsOverlayLoader.ensureOverlayLoaded(this.kIndicatorOverlay, () => {
+      if (!this._placeholder) {
+        aCallback(false);
+      } else {
+        let element = DownloadsIndicatorView.indicator || this._placeholder;
+        aCallback(isElementVisible(element.parentNode));
+      }
+    });
+  },
+
+  /**
+   * Indicates whether we should try and show the indicator temporarily as an
+   * anchor for the panel, even if the indicator would be hidden by default.
+   */
+  _anchorRequested: false,
+
+  /**
+   * Ensures that there is an anchor available for the panel.
+   *
+   * @param aCallback
+   *        Called when the anchor is available, passing the element where the
+   *        panel should be anchored, or null if an anchor is not available (for
+   *        example because both the tab bar and the navigation bar are hidden).
+   */
+  getAnchor(aCallback) {
+    // Do not allow anchoring the panel to the element while customizing.
+    if (this._customizing) {
+      aCallback(null);
+      return;
+    }
+
+    DownloadsOverlayLoader.ensureOverlayLoaded(this.kIndicatorOverlay, () => {
+      this._anchorRequested = true;
+      aCallback(this._getAnchorInternal());
+    });
+  },
+
+  /**
+   * Allows the temporary anchor to be hidden.
+   */
+  releaseAnchor() {
+    this._anchorRequested = false;
+    this._getAnchorInternal();
+  },
+
+  get _tabsToolbar() {
+    delete this._tabsToolbar;
+    return this._tabsToolbar = document.getElementById("TabsToolbar");
+  },
+
+  get _navBar() {
+    delete this._navBar;
+    return this._navBar = document.getElementById("nav-bar");
+  }
+};
+
+Object.defineProperty(this, "DownloadsButton", {
+  value: DownloadsButton,
+  enumerable: true,
+  writable: false
+});
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadsIndicatorView
+
+/**
+ * Builds and updates the actual downloads status widget, responding to changes
+ * in the global status data, or provides a neutral view if the indicator is
+ * removed from the toolbars and only used as a temporary anchor.  In addition,
+ * handles the user interaction events raised by the widget.
+ */
+const DownloadsIndicatorView = {
+  /**
+   * True when the view is connected with the underlying downloads data.
+   */
+  _initialized: false,
+
+  /**
+   * True when the user interface elements required to display the indicator
+   * have finished loading in the browser window, and can be referenced.
+   */
+  _operational: false,
+
+  /**
+   * Prepares the downloads indicator to be displayed.
+   */
+  ensureInitialized() {
+    if (this._initialized) {
+      return;
+    }
+    this._initialized = true;
+
+    window.addEventListener("unload", this.onWindowUnload, false);
+    DownloadsCommon.getIndicatorData(window).addView(this);
+  },
+
+  /**
+   * Frees the internal resources related to the indicator.
+   */
+  ensureTerminated() {
+    if (!this._initialized) {
+      return;
+    }
+    this._initialized = false;
+
+    window.removeEventListener("unload", this.onWindowUnload, false);
+    DownloadsCommon.getIndicatorData(window).removeView(this);
+
+    // Reset the view properties, so that a neutral indicator is displayed if we
+    // are visible only temporarily as an anchor.
+    this.counter = "";
+    this.percentComplete = 0;
+    this.paused = false;
+    this.attention = DownloadsCommon.ATTENTION_NONE;
+  },
+
+  /**
+   * Ensures that the user interface elements required to display the indicator
+   * are loaded, then invokes the given callback.
+   */
+  _ensureOperational(aCallback) {
+    if (this._operational) {
+      if (aCallback) {
+        aCallback();
+      }
+      return;
+    }
+
+    // If we don't have a _placeholder, there's no chance that the overlay
+    // will load correctly: bail (and don't set _operational to true!)
+    if (!DownloadsButton._placeholder) {
+      return;
+    }
+
+    DownloadsOverlayLoader.ensureOverlayLoaded(
+      DownloadsButton.kIndicatorOverlay,
+      () => {
+        this._operational = true;
+
+        // If the view is initialized, we need to update the elements now that
+        // they are finally available in the document.
+        if (this._initialized) {
+          DownloadsCommon.getIndicatorData(window).refreshView(this);
+        }
+
+        if (aCallback) {
+          aCallback();
+        }
+      });
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Direct control functions
+
+  /**
+   * Set while we are waiting for a notification to fade out.
+   */
+  _notificationTimeout: null,
+
+  /**
+   * Check if the panel containing aNode is open.
+   * @param aNode
+   *        the node whose panel we're interested in.
+   */
+  _isAncestorPanelOpen(aNode) {
+    while (aNode && aNode.localName != "panel") {
+      aNode = aNode.parentNode;
+    }
+    return aNode && aNode.state == "open";
+  },
+
+  /**
+   * If the status indicator is visible in its assigned position, shows for a
+   * brief time a visual notification of a relevant event, like a new download.
+   *
+   * @param aType
+   *        Set to "start" for new downloads, "finish" for completed downloads.
+   */
+  showEventNotification(aType) {
+    if (!this._initialized) {
+      return;
+    }
+
+    if (!DownloadsCommon.animateNotifications) {
+      return;
+    }
+
+    // No need to show visual notification if the panel is visible.
+    if (DownloadsPanel.isPanelShowing) {
+      return;
+    }
+
+    let anchor = DownloadsButton._placeholder;
+    let widgetGroup = CustomizableUI.getWidget("downloads-button");
+    let widget = widgetGroup.forWindow(window);
+    if (widget.overflowed || widgetGroup.areaType == CustomizableUI.TYPE_MENU_PANEL) {
+      if (anchor && this._isAncestorPanelOpen(anchor)) {
+        // If the containing panel is open, don't do anything, because the
+        // notification would appear under the open panel. See
+        // https://bugzilla.mozilla.org/show_bug.cgi?id=984023
+        return;
+      }
+
+      // Otherwise, try to use the anchor of the panel:
+      anchor = widget.anchor;
+    }
+    if (!anchor || !isElementVisible(anchor.parentNode)) {
+      // Our container isn't visible, so can't show the animation:
+      return;
+    }
+
+    if (this._notificationTimeout) {
+      clearTimeout(this._notificationTimeout);
+    }
+
+    // The notification element is positioned to show in the same location as
+    // the downloads button. It's not in the downloads button itself in order to
+    // be able to anchor the notification elsewhere if required, and to ensure
+    // the notification isn't clipped by overflow properties of the anchor's
+    // container.
+    let notifier = this.notifier;
+    if (notifier.style.transform == '') {
+      let anchorRect = anchor.getBoundingClientRect();
+      let notifierRect = notifier.getBoundingClientRect();
+      let topDiff = anchorRect.top - notifierRect.top;
+      let leftDiff = anchorRect.left - notifierRect.left;
+      let heightDiff = anchorRect.height - notifierRect.height;
+      let widthDiff = anchorRect.width - notifierRect.width;
+      let translateX = (leftDiff + .5 * widthDiff) + "px";
+      let translateY = (topDiff + .5 * heightDiff) + "px";
+      notifier.style.transform = "translate(" +  translateX + ", " + translateY + ")";
+    }
+    notifier.setAttribute("notification", aType);
+    this._notificationTimeout = setTimeout(() => {
+      notifier.removeAttribute("notification");
+      notifier.style.transform = '';
+    }, 1000);
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// Callback functions from DownloadsIndicatorData
+
+  /**
+   * Indicates whether the indicator should be shown because there are some
+   * downloads to be displayed.
+   */
+  set hasDownloads(aValue) {
+    if (this._hasDownloads != aValue || (!this._operational && aValue)) {
+      this._hasDownloads = aValue;
+
+      // If there is at least one download, ensure that the view elements are
+      if (aValue) {
+        this._ensureOperational();
+      }
+    }
+    return aValue;
+  },
+  get hasDownloads() {
+    return this._hasDownloads;
+  },
+  _hasDownloads: false,
+
+  /**
+   * Status text displayed in the indicator.  If this is set to an empty value,
+   * then the small downloads icon is displayed instead of the text.
+   */
+  set counter(aValue) {
+    if (!this._operational) {
+      return this._counter;
+    }
+
+    if (this._counter !== aValue) {
+      this._counter = aValue;
+      if (this._counter)
+        this.indicator.setAttribute("counter", "true");
+      else
+        this.indicator.removeAttribute("counter");
+      // We have to set the attribute instead of using the property because the
+      // XBL binding isn't applied if the element is invisible for any reason.
+      this._indicatorCounter.setAttribute("value", aValue);
+    }
+    return aValue;
+  },
+  _counter: null,
+
+  /**
+   * Progress indication to display, from 0 to 100, or -1 if unknown.  The
+   * progress bar is hidden if the current progress is unknown and no status
+   * text is set in the "counter" property.
+   */
+  set percentComplete(aValue) {
+    if (!this._operational) {
+      return this._percentComplete;
+    }
+
+    if (this._percentComplete !== aValue) {
+      this._percentComplete = aValue;
+      if (this._percentComplete >= 0)
+        this.indicator.setAttribute("progress", "true");
+      else
+        this.indicator.removeAttribute("progress");
+      // We have to set the attribute instead of using the property because the
+      // XBL binding isn't applied if the element is invisible for any reason.
+      this._indicatorProgress.setAttribute("value", Math.max(aValue, 0));
+    }
+    return aValue;
+  },
+  _percentComplete: null,
+
+  /**
+   * Indicates whether the progress won't advance because of a paused state.
+   * Setting this property forces a paused progress bar to be displayed, even if
+   * the current progress information is unavailable.
+   */
+  set paused(aValue) {
+    if (!this._operational) {
+      return this._paused;
+    }
+
+    if (this._paused != aValue) {
+      this._paused = aValue;
+      if (this._paused) {
+        this.indicator.setAttribute("paused", "true")
+      } else {
+        this.indicator.removeAttribute("paused");
+      }
+    }
+    return aValue;
+  },
+  _paused: false,
+
+  /**
+   * Set when the indicator should draw user attention to itself.
+   */
+  set attention(aValue) {
+    if (!this._operational) {
+      return this._attention;
+    }
+
+    if (this._attention != aValue) {
+      this._attention = aValue;
+
+      // Check if the downloads button is in the menu panel, to determine which
+      // button needs to get a badge.
+      let widgetGroup = CustomizableUI.getWidget("downloads-button");
+      let inMenu = widgetGroup.areaType == CustomizableUI.TYPE_MENU_PANEL;
+
+      if (aValue == DownloadsCommon.ATTENTION_NONE) {
+        this.indicator.removeAttribute("attention");
+        if (inMenu) {
+          gMenuButtonBadgeManager.removeBadge(gMenuButtonBadgeManager.BADGEID_DOWNLOAD);
+        }
+      } else {
+        this.indicator.setAttribute("attention", aValue);
+        if (inMenu) {
+          let badgeClass = "download-" + aValue;
+          gMenuButtonBadgeManager.addBadge(gMenuButtonBadgeManager.BADGEID_DOWNLOAD, badgeClass);
+        }
+      }
+    }
+    return aValue;
+  },
+  _attention: DownloadsCommon.ATTENTION_NONE,
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// User interface event functions
+
+  onWindowUnload() {
+    // This function is registered as an event listener, we can't use "this".
+    DownloadsIndicatorView.ensureTerminated();
+  },
+
+  onCommand(aEvent) {
+    // If the downloads button is in the menu panel, open the Library
+    let widgetGroup = CustomizableUI.getWidget("downloads-button");
+    if (widgetGroup.areaType == CustomizableUI.TYPE_MENU_PANEL) {
+      DownloadsPanel.showDownloadsHistory();
+    } else {
+      DownloadsPanel.showPanel();
+    }
+
+    aEvent.stopPropagation();
+  },
+
+  onDragOver(aEvent) {
+    browserDragAndDrop.dragOver(aEvent);
+  },
+
+  onDrop(aEvent) {
+    let dt = aEvent.dataTransfer;
+    // If dragged item is from our source, do not try to
+    // redownload already downloaded file.
+    if (dt.mozGetDataAt("application/x-moz-file", 0))
+      return;
+
+    let links = browserDragAndDrop.dropLinks(aEvent);
+    if (!links.length)
+      return;
+    let sourceDoc = dt.mozSourceNode ? dt.mozSourceNode.ownerDocument : document;
+    let handled = false;
+    for (let link of links) {
+      if (link.url.startsWith("about:"))
+        continue;
+      saveURL(link.url, link.name, null, true, true, null, sourceDoc);
+      handled = true;
+    }
+    if (handled) {
+      aEvent.preventDefault();
+    }
+  },
+
+  _indicator: null,
+  __indicatorCounter: null,
+  __indicatorProgress: null,
+
+  /**
+   * Returns a reference to the main indicator element, or null if the element
+   * is not present in the browser window yet.
+   */
+  get indicator() {
+    if (this._indicator) {
+      return this._indicator;
+    }
+
+    let indicator = document.getElementById("downloads-button");
+    if (!indicator || indicator.getAttribute("indicator") != "true") {
+      return null;
+    }
+
+    return this._indicator = indicator;
+  },
+
+  get indicatorAnchor() {
+    let widget = CustomizableUI.getWidget("downloads-button")
+                               .forWindow(window);
+    if (widget.overflowed) {
+      return widget.anchor;
+    }
+    return document.getElementById("downloads-indicator-anchor");
+  },
+
+  get _indicatorCounter() {
+    return this.__indicatorCounter ||
+      (this.__indicatorCounter = document.getElementById("downloads-indicator-counter"));
+  },
+
+  get _indicatorProgress() {
+    return this.__indicatorProgress ||
+      (this.__indicatorProgress = document.getElementById("downloads-indicator-progress"));
+  },
+
+  get notifier() {
+    return this._notifier ||
+      (this._notifier = document.getElementById("downloads-notification-anchor"));
+  },
+
+  _onCustomizedAway() {
+    this._indicator = null;
+    this.__indicatorCounter = null;
+    this.__indicatorProgress = null;
+  },
+
+  afterCustomize() {
+    // If the cached indicator is not the one currently in the document,
+    // invalidate our references
+    if (this._indicator != document.getElementById("downloads-button")) {
+      this._onCustomizedAway();
+      this._operational = false;
+      this.ensureTerminated();
+      this.ensureInitialized();
+    }
+  },
+};
+
+Object.defineProperty(this, "DownloadsIndicatorView", {
+  value: DownloadsIndicatorView,
+  enumerable: true,
+  writable: false
+});
diff --git a/browser/components/downloads/content/indicatorOverlay.xul b/browser/components/downloads/content/indicatorOverlay.xul
new file mode 100644
index 000000000..07987c88c
--- /dev/null
+++ b/browser/components/downloads/content/indicatorOverlay.xul
@@ -0,0 +1,36 @@
+<?xml version="1.0"?>
+<!-- -*- Mode: HTML; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- -->
+<!-- vim: set ts=2 et sw=2 tw=80: -->
+
+<!-- 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 overlay [
+  <!ENTITY % browserDTD SYSTEM "chrome://browser/locale/browser.dtd" >
+  %browserDTD;
+]>
+
+<overlay xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+         id="indicatorOverlay">
+
+  <!-- We dynamically add the stack with the progress meter and notification icon,
+       originally loaded lazily because of performance reasons, to the existing
+       downloads-button. -->
+  <toolbarbutton id="downloads-button" indicator="true">
+    <!-- The panel's anchor area is smaller than the outer button, but must
+         always be visible and must not move or resize when the indicator
+         state changes, otherwise the panel could change its position or lose
+         its arrow unexpectedly. -->
+    <stack id="downloads-indicator-anchor"
+           consumeanchor="downloads-button">
+      <vbox id="downloads-indicator-progress-area" pack="center">
+        <description id="downloads-indicator-counter"/>
+        <progressmeter id="downloads-indicator-progress" class="plain"
+                       min="0" max="100"/>
+      </vbox>
+      <vbox id="downloads-indicator-icon"/>
+    </stack>
+  </toolbarbutton>
+</overlay>
diff --git a/browser/components/downloads/jar.mn b/browser/components/downloads/jar.mn
new file mode 100644
index 000000000..2663454fa
--- /dev/null
+++ b/browser/components/downloads/jar.mn
@@ -0,0 +1,16 @@
+# 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/downloads/download.xml           (content/download.xml)
+        content/browser/downloads/downloads.css          (content/downloads.css)
+        content/browser/downloads/downloads.js           (content/downloads.js)
+*       content/browser/downloads/downloadsOverlay.xul   (content/downloadsOverlay.xul)
+        content/browser/downloads/indicator.js           (content/indicator.js)
+        content/browser/downloads/indicatorOverlay.xul   (content/indicatorOverlay.xul)
+*       content/browser/downloads/allDownloadsViewOverlay.xul (content/allDownloadsViewOverlay.xul)
+        content/browser/downloads/allDownloadsViewOverlay.js  (content/allDownloadsViewOverlay.js)
+*       content/browser/downloads/contentAreaDownloadsView.xul (content/contentAreaDownloadsView.xul)
+        content/browser/downloads/contentAreaDownloadsView.js  (content/contentAreaDownloadsView.js)
+        content/browser/downloads/contentAreaDownloadsView.css (content/contentAreaDownloadsView.css)
diff --git a/browser/components/downloads/moz.build b/browser/components/downloads/moz.build
new file mode 100644
index 000000000..2b06a6465
--- /dev/null
+++ b/browser/components/downloads/moz.build
@@ -0,0 +1,22 @@
+# -*- 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/.
+
+with Files('*'):
+    BUG_COMPONENT = ('Firefox', 'Downloads Panel')
+
+XPCSHELL_TESTS_MANIFESTS += ['test/unit/xpcshell.ini']
+BROWSER_CHROME_MANIFESTS += ['test/browser/browser.ini']
+
+JAR_MANIFESTS += ['jar.mn']
+
+EXTRA_JS_MODULES += [
+    'DownloadsCommon.jsm',
+    'DownloadsTaskbar.jsm',
+    'DownloadsViewUI.jsm',
+]
+
+with Files('**'):
+    BUG_COMPONENT = ('Firefox', 'Downloads Panel')
diff --git a/browser/components/downloads/test/browser/.eslintrc.js b/browser/components/downloads/test/browser/.eslintrc.js
new file mode 100644
index 000000000..7c8021192
--- /dev/null
+++ b/browser/components/downloads/test/browser/.eslintrc.js
@@ -0,0 +1,7 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "../../../../../testing/mochitest/browser.eslintrc.js"
+  ]
+};
diff --git a/browser/components/downloads/test/browser/browser.ini b/browser/components/downloads/test/browser/browser.ini
new file mode 100644
index 000000000..76f026c78
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser.ini
@@ -0,0 +1,15 @@
+[DEFAULT]
+support-files = head.js
+
+[browser_basic_functionality.js]
+[browser_first_download_panel.js]
+skip-if = os == "linux" # Bug 949434
+[browser_overflow_anchor.js]
+skip-if = os == "linux" # Bug 952422
+[browser_confirm_unblock_download.js]
+[browser_iframe_gone_mid_download.js]
+[browser_indicatorDrop.js]
+[browser_libraryDrop.js]
+[browser_downloads_panel_block.js]
+[browser_downloads_panel_footer.js]
+[browser_downloads_panel_height.js]
diff --git a/browser/components/downloads/test/browser/browser_basic_functionality.js b/browser/components/downloads/test/browser/browser_basic_functionality.js
new file mode 100644
index 000000000..564a344a7
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_basic_functionality.js
@@ -0,0 +1,56 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+registerCleanupFunction(function*() {
+  yield task_resetState();
+});
+
+/**
+ * Make sure the downloads panel can display items in the right order and
+ * contains the expected data.
+ */
+add_task(function* test_basic_functionality() {
+  // Display one of each download state.
+  const DownloadData = [
+    { state: nsIDM.DOWNLOAD_NOTSTARTED },
+    { state: nsIDM.DOWNLOAD_PAUSED },
+    { state: nsIDM.DOWNLOAD_FINISHED },
+    { state: nsIDM.DOWNLOAD_FAILED },
+    { state: nsIDM.DOWNLOAD_CANCELED },
+  ];
+
+  // Wait for focus first
+  yield promiseFocus();
+
+  // Ensure that state is reset in case previous tests didn't finish.
+  yield task_resetState();
+
+  // For testing purposes, show all the download items at once.
+  var originalCountLimit = DownloadsView.kItemCountLimit;
+  DownloadsView.kItemCountLimit = DownloadData.length;
+  registerCleanupFunction(function () {
+    DownloadsView.kItemCountLimit = originalCountLimit;
+  });
+
+  // Populate the downloads database with the data required by this test.
+  yield task_addDownloads(DownloadData);
+
+  // Open the user interface and wait for data to be fully loaded.
+  yield task_openPanel();
+
+  // Test item data and count.  This also tests the ordering of the display.
+  let richlistbox = document.getElementById("downloadsListBox");
+  /* disabled for failing intermittently (bug 767828)
+    is(richlistbox.children.length, DownloadData.length,
+       "There is the correct number of richlistitems");
+  */
+  let itemCount = richlistbox.children.length;
+  for (let i = 0; i < itemCount; i++) {
+    let element = richlistbox.children[itemCount - i - 1];
+    let download = DownloadsView.itemForElement(element).download;
+    is(DownloadsCommon.stateOfDownload(download), DownloadData[i].state,
+       "Download states match up");
+  }
+});
diff --git a/browser/components/downloads/test/browser/browser_confirm_unblock_download.js b/browser/components/downloads/test/browser/browser_confirm_unblock_download.js
new file mode 100644
index 000000000..8ba37ba64
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_confirm_unblock_download.js
@@ -0,0 +1,92 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Tests the dialog which allows the user to unblock a downloaded file.
+
+registerCleanupFunction(() => {});
+
+function* assertDialogResult({ args, buttonToClick, expectedResult }) {
+  promiseAlertDialogOpen(buttonToClick);
+  is(yield DownloadsCommon.confirmUnblockDownload(args), expectedResult);
+}
+
+/**
+ * Tests the "unblock" dialog, for each of the possible verdicts.
+ */
+add_task(function* test_unblock_dialog_unblock() {
+  for (let verdict of [Downloads.Error.BLOCK_VERDICT_MALWARE,
+                       Downloads.Error.BLOCK_VERDICT_POTENTIALLY_UNWANTED,
+                       Downloads.Error.BLOCK_VERDICT_UNCOMMON]) {
+    let args = { verdict, window, dialogType: "unblock" };
+
+    // Test both buttons.
+    yield assertDialogResult({
+      args,
+      buttonToClick: "accept",
+      expectedResult: "unblock",
+    });
+    yield assertDialogResult({
+      args,
+      buttonToClick: "cancel",
+      expectedResult: "cancel",
+    });
+  }
+});
+
+/**
+ * Tests the "chooseUnblock" dialog for potentially unwanted downloads.
+ */
+add_task(function* test_chooseUnblock_dialog() {
+  let args = {
+    verdict: Downloads.Error.BLOCK_VERDICT_POTENTIALLY_UNWANTED,
+    window,
+    dialogType: "chooseUnblock",
+  };
+
+  // Test each of the three buttons.
+  yield assertDialogResult({
+    args,
+    buttonToClick: "accept",
+    expectedResult: "unblock",
+  });
+  yield assertDialogResult({
+    args,
+    buttonToClick: "cancel",
+    expectedResult: "cancel",
+  });
+  yield assertDialogResult({
+    args,
+    buttonToClick: "extra1",
+    expectedResult: "confirmBlock",
+  });
+});
+
+/**
+ * Tests the "chooseOpen" dialog for uncommon downloads.
+ */
+add_task(function* test_chooseOpen_dialog() {
+  let args = {
+    verdict: Downloads.Error.BLOCK_VERDICT_UNCOMMON,
+    window,
+    dialogType: "chooseOpen",
+  };
+
+  // Test each of the three buttons.
+  yield assertDialogResult({
+    args,
+    buttonToClick: "accept",
+    expectedResult: "open",
+  });
+  yield assertDialogResult({
+    args,
+    buttonToClick: "cancel",
+    expectedResult: "cancel",
+  });
+  yield assertDialogResult({
+    args,
+    buttonToClick: "extra1",
+    expectedResult: "confirmBlock",
+  });
+});
diff --git a/browser/components/downloads/test/browser/browser_downloads_panel_block.js b/browser/components/downloads/test/browser/browser_downloads_panel_block.js
new file mode 100644
index 000000000..05056e842
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_downloads_panel_block.js
@@ -0,0 +1,183 @@
+"use strict";
+
+add_task(function* mainTest() {
+  yield task_resetState();
+
+  let verdicts = [
+    Downloads.Error.BLOCK_VERDICT_UNCOMMON,
+    Downloads.Error.BLOCK_VERDICT_MALWARE,
+    Downloads.Error.BLOCK_VERDICT_POTENTIALLY_UNWANTED,
+  ];
+  yield task_addDownloads(verdicts.map(v => makeDownload(v)));
+
+  // Check that the richlistitem for each download is correct.
+  for (let i = 0; i < verdicts.length; i++) {
+    yield openPanel();
+
+    // The current item is always the first one in the listbox since each
+    // iteration of this loop removes the item at the end.
+    let item = DownloadsView.richListBox.firstChild;
+
+    // Open the panel and click the item to show the subview.
+    EventUtils.sendMouseEvent({ type: "click" }, item);
+    yield promiseSubviewShown(true);
+
+    // Items are listed in newest-to-oldest order, so e.g. the first item's
+    // verdict is the last element in the verdicts array.
+    Assert.ok(DownloadsBlockedSubview.subview.getAttribute("verdict"),
+              verdicts[verdicts.count - i - 1]);
+
+    // Click the sliver of the main view that's still showing on the left to go
+    // back to it.
+    EventUtils.synthesizeMouse(DownloadsPanel.panel, 10, 10, {}, window);
+    yield promiseSubviewShown(false);
+
+    // Show the subview again.
+    EventUtils.sendMouseEvent({ type: "click" }, item);
+    yield promiseSubviewShown(true);
+
+    // Click the Open button.  The download should be unblocked and then opened,
+    // i.e., unblockAndOpenDownload() should be called on the item.  The panel
+    // should also be closed as a result, so wait for that too.
+    let unblockOpenPromise = promiseUnblockAndOpenDownloadCalled(item);
+    let hidePromise = promisePanelHidden();
+    EventUtils.synthesizeMouse(DownloadsBlockedSubview.elements.openButton,
+                               10, 10, {}, window);
+    yield unblockOpenPromise;
+    yield hidePromise;
+
+    window.focus();
+    yield SimpleTest.promiseFocus(window);
+
+    // Reopen the panel and show the subview again.
+    yield openPanel();
+
+    EventUtils.sendMouseEvent({ type: "click" }, item);
+    yield promiseSubviewShown(true);
+
+    // Click the Remove button.  The panel should close and the item should be
+    // removed from it.
+    EventUtils.synthesizeMouse(DownloadsBlockedSubview.elements.deleteButton,
+                               10, 10, {}, window);
+    yield promisePanelHidden();
+    yield openPanel();
+
+    Assert.ok(!item.parentNode);
+    DownloadsPanel.hidePanel();
+    yield promisePanelHidden();
+  }
+
+  yield task_resetState();
+});
+
+function* openPanel() {
+  // This function is insane but something intermittently causes the panel to be
+  // closed as soon as it's opening on Linux ASAN.  Maybe it would also happen
+  // on other build machines if the test ran often enough.  Not only is the
+  // panel closed, it's closed while it's opening, leaving DownloadsPanel._state
+  // such that when you try to open the panel again, it thinks it's already
+  // open, but it's not.  The result is that the test times out.
+  //
+  // What this does is call DownloadsPanel.showPanel over and over again until
+  // the panel is really open.  There are a few wrinkles:
+  //
+  // (1) When panel.state is "open", check four more times (for a total of five)
+  // before returning to make the panel stays open.
+  // (2) If the panel is not open, check the _state.  It should be either
+  // kStateUninitialized or kStateHidden.  If it's not, then the panel is in the
+  // process of opening -- or maybe it's stuck in that process -- so reset the
+  // _state to kStateHidden.
+  // (3) If the _state is not kStateUninitialized or kStateHidden, then it may
+  // actually be properly opening and not stuck at all.  To avoid always closing
+  // the panel while it's properly opening, use an exponential backoff mechanism
+  // for retries.
+  //
+  // If all that fails, then the test will time out, but it would have timed out
+  // anyway.
+
+  yield promiseFocus();
+  yield new Promise(resolve => {
+    let verifyCount = 5;
+    let backoff = 0;
+    let iBackoff = 0;
+    let interval = setInterval(() => {
+      if (DownloadsPanel.panel && DownloadsPanel.panel.state == "open") {
+        if (verifyCount > 0) {
+          verifyCount--;
+        } else {
+          clearInterval(interval);
+          resolve();
+        }
+      } else {
+        if (iBackoff < backoff) {
+          // Keep backing off before trying again.
+          iBackoff++;
+        } else {
+          // Try (or retry) opening the panel.
+          verifyCount = 5;
+          backoff = Math.max(1, 2 * backoff);
+          iBackoff = 0;
+          if (DownloadsPanel._state != DownloadsPanel.kStateUninitialized) {
+            DownloadsPanel._state = DownloadsPanel.kStateHidden;
+          }
+          DownloadsPanel.showPanel();
+        }
+      }
+    }, 100);
+  });
+}
+
+function promisePanelHidden() {
+  return new Promise(resolve => {
+    if (!DownloadsPanel.panel || DownloadsPanel.panel.state == "closed") {
+      resolve();
+      return;
+    }
+    DownloadsPanel.panel.addEventListener("popuphidden", function onHidden() {
+      DownloadsPanel.panel.removeEventListener("popuphidden", onHidden);
+      setTimeout(resolve, 0);
+    });
+  });
+}
+
+function makeDownload(verdict) {
+  return {
+    state: nsIDM.DOWNLOAD_DIRTY,
+    hasBlockedData: true,
+    errorObj: {
+      result: Components.results.NS_ERROR_FAILURE,
+      message: "Download blocked.",
+      becauseBlocked: true,
+      becauseBlockedByReputationCheck: true,
+      reputationCheckVerdict:  verdict,
+    },
+  };
+}
+
+function promiseSubviewShown(shown) {
+  // More terribleness, but I'm tired of fighting intermittent timeouts on try.
+  // Just poll for the subview and wait a second before resolving the promise.
+  return new Promise(resolve => {
+    let interval = setInterval(() => {
+      if (shown == DownloadsBlockedSubview.view.showingSubView &&
+          !DownloadsBlockedSubview.view._transitioning) {
+        clearInterval(interval);
+        setTimeout(resolve, 1000);
+        return;
+      }
+    }, 0);
+  });
+}
+
+function promiseUnblockAndOpenDownloadCalled(item) {
+  return new Promise(resolve => {
+    let realFn = item._shell.unblockAndOpenDownload;
+    item._shell.unblockAndOpenDownload = () => {
+      item._shell.unblockAndOpenDownload = realFn;
+      resolve();
+      // unblockAndOpenDownload returns a promise (that's resolved when the file
+      // is opened).
+      return Promise.resolve();
+    };
+  });
+}
diff --git a/browser/components/downloads/test/browser/browser_downloads_panel_footer.js b/browser/components/downloads/test/browser/browser_downloads_panel_footer.js
new file mode 100644
index 000000000..4083dde98
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_downloads_panel_footer.js
@@ -0,0 +1,95 @@
+"use strict";
+
+function *task_openDownloadsSubPanel() {
+  let downloadSubPanel = document.getElementById("downloadSubPanel");
+  let popupShownPromise = BrowserTestUtils.waitForEvent(downloadSubPanel, "popupshown");
+
+  let downloadsDropmarker = document.getElementById("downloadsFooterDropmarker");
+  EventUtils.synthesizeMouseAtCenter(downloadsDropmarker, {}, window);
+
+  yield popupShownPromise;
+}
+
+add_task(function* test_openDownloadsFolder() {
+  yield SpecialPowers.pushPrefEnv({"set": [["browser.download.showPanelDropmarker", true]]});
+  yield task_openPanel();
+
+  yield task_openDownloadsSubPanel();
+
+  yield new Promise(resolve => {
+    sinon.stub(DownloadsCommon, "showDirectory", file => {
+      resolve(Downloads.getPreferredDownloadsDirectory().then(downloadsPath => {
+        is(file.path, downloadsPath, "Check the download folder path.");
+      }));
+    });
+
+    let itemOpenDownloadsFolder =
+      document.getElementById("downloadsDropdownItemOpenDownloadsFolder");
+    EventUtils.synthesizeMouseAtCenter(itemOpenDownloadsFolder, {}, window);
+  });
+
+  yield task_resetState();
+});
+
+add_task(function* test_clearList() {
+  const kTestCases = [{
+    downloads: [
+      { state: nsIDM.DOWNLOAD_NOTSTARTED },
+      { state: nsIDM.DOWNLOAD_FINISHED },
+      { state: nsIDM.DOWNLOAD_FAILED },
+      { state: nsIDM.DOWNLOAD_CANCELED },
+    ],
+    expectClearListShown: true,
+    expectedItemNumber: 0,
+  },{
+    downloads: [
+      { state: nsIDM.DOWNLOAD_NOTSTARTED },
+      { state: nsIDM.DOWNLOAD_FINISHED },
+      { state: nsIDM.DOWNLOAD_FAILED },
+      { state: nsIDM.DOWNLOAD_PAUSED },
+      { state: nsIDM.DOWNLOAD_CANCELED },
+    ],
+    expectClearListShown: true,
+    expectedItemNumber: 1,
+  },{
+    downloads: [
+      { state: nsIDM.DOWNLOAD_PAUSED },
+    ],
+    expectClearListShown: false,
+    expectedItemNumber: 1,
+  }];
+
+  for (let testCase of kTestCases) {
+    yield verify_clearList(testCase);
+  }
+});
+
+function *verify_clearList(testCase) {
+  let downloads = testCase.downloads;
+  yield task_addDownloads(downloads);
+
+  yield task_openPanel();
+  is(DownloadsView._downloads.length, downloads.length,
+    "Expect the number of download items");
+
+  yield task_openDownloadsSubPanel();
+
+  let itemClearList = document.getElementById("downloadsDropdownItemClearList");
+  let itemNumberPromise = BrowserTestUtils.waitForCondition(() => {
+    return DownloadsView._downloads.length === testCase.expectedItemNumber;
+  });
+  if (testCase.expectClearListShown) {
+    isnot("true", itemClearList.getAttribute("hidden"),
+      "Should show Clear Preview Panel button");
+    EventUtils.synthesizeMouseAtCenter(itemClearList, {}, window);
+  } else {
+    is("true", itemClearList.getAttribute("hidden"),
+      "Should not show Clear Preview Panel button");
+  }
+
+  yield itemNumberPromise;
+  is(DownloadsView._downloads.length, testCase.expectedItemNumber,
+    "Download items remained.");
+
+  yield task_resetState();
+}
diff --git a/browser/components/downloads/test/browser/browser_downloads_panel_height.js b/browser/components/downloads/test/browser/browser_downloads_panel_height.js
new file mode 100644
index 000000000..1638e4f0e
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_downloads_panel_height.js
@@ -0,0 +1,29 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * This test exists because we use a <panelmultiview> element and it handles
+ * some of the height changes for us. We need to verify that the height is
+ * updated correctly if downloads are removed while the panel is hidden.
+ */
+add_task(function* test_height_reduced_after_removal() {
+  yield task_addDownloads([
+    { state: nsIDM.DOWNLOAD_FINISHED },
+  ]);
+
+  yield task_openPanel();
+  let panel = document.getElementById("downloadsPanel");
+  let heightBeforeRemoval = panel.getBoundingClientRect().height;
+
+  // We want to close the panel before we remove the download from the list.
+  DownloadsPanel.hidePanel();
+  yield task_resetState();
+
+  yield task_openPanel();
+  let heightAfterRemoval = panel.getBoundingClientRect().height;
+  Assert.greater(heightBeforeRemoval, heightAfterRemoval);
+
+  yield task_resetState();
+});
diff --git a/browser/components/downloads/test/browser/browser_first_download_panel.js b/browser/components/downloads/test/browser/browser_first_download_panel.js
new file mode 100644
index 000000000..2cd871360
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_first_download_panel.js
@@ -0,0 +1,57 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Make sure the downloads panel only opens automatically on the first
+ * download it notices. All subsequent downloads, even across sessions, should
+ * not open the panel automatically.
+ */
+add_task(function* test_first_download_panel() {
+  // Clear the download panel has shown preference first as this test is used to
+  // verify this preference's behaviour.
+  let oldPrefValue = Services.prefs.getBoolPref("browser.download.panel.shown");
+  Services.prefs.setBoolPref("browser.download.panel.shown", false);
+
+  registerCleanupFunction(function*() {
+    // Clean up when the test finishes.
+    yield task_resetState();
+
+    // Set the preference instead of clearing it afterwards to ensure the
+    // right value is used no matter what the default was. This ensures the
+    // panel doesn't appear and affect other tests.
+    Services.prefs.setBoolPref("browser.download.panel.shown", oldPrefValue);
+  });
+
+  // Ensure that state is reset in case previous tests didn't finish.
+  yield task_resetState();
+
+  // With this set to false, we should automatically open the panel the first
+  // time a download is started.
+  DownloadsCommon.getData(window).panelHasShownBefore = false;
+
+  let promise = promisePanelOpened();
+  DownloadsCommon.getData(window)._notifyDownloadEvent("start");
+  yield promise;
+
+  // If we got here, that means the panel opened.
+  DownloadsPanel.hidePanel();
+
+  ok(DownloadsCommon.getData(window).panelHasShownBefore,
+     "Should have recorded that the panel was opened on a download.")
+
+  // Next, make sure that if we start another download, we don't open the
+  // panel automatically.
+  let originalOnPopupShown = DownloadsPanel.onPopupShown;
+  DownloadsPanel.onPopupShown = function () {
+    originalOnPopupShown.apply(this, arguments);
+    ok(false, "Should not have opened the downloads panel.");
+  };
+
+  DownloadsCommon.getData(window)._notifyDownloadEvent("start");
+
+  // Wait 2 seconds to ensure that the panel does not open.
+  yield new Promise(resolve => setTimeout(resolve, 2000));
+  DownloadsPanel.onPopupShown = originalOnPopupShown;
+});
diff --git a/browser/components/downloads/test/browser/browser_iframe_gone_mid_download.js b/browser/components/downloads/test/browser/browser_iframe_gone_mid_download.js
new file mode 100644
index 000000000..ebdd4f9af
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_iframe_gone_mid_download.js
@@ -0,0 +1,62 @@
+const SAVE_PER_SITE_PREF = "browser.download.lastDir.savePerSite";
+
+function test_deleted_iframe(perSitePref, windowOptions={}) {
+  return function*() {
+    Services.prefs.setBoolPref(SAVE_PER_SITE_PREF, perSitePref);
+    let {DownloadLastDir} = Cu.import("resource://gre/modules/DownloadLastDir.jsm", {});
+
+    let win = yield promiseOpenAndLoadWindow(windowOptions);
+    let tab = win.gBrowser.addTab();
+    yield promiseTabLoadEvent(tab, "about:mozilla");
+
+    let doc = tab.linkedBrowser.contentDocument;
+    let iframe = doc.createElement("iframe");
+    doc.body.appendChild(iframe);
+
+    ok(iframe.contentWindow, "iframe should have a window");
+    let gDownloadLastDir = new DownloadLastDir(iframe.contentWindow);
+    let cw = iframe.contentWindow;
+    let promiseIframeWindowGone = new Promise((resolve, reject) => {
+      Services.obs.addObserver(function obs(subject, topic) {
+        if (subject == cw) {
+          Services.obs.removeObserver(obs, topic);
+          resolve();
+        }
+      }, "dom-window-destroyed", false);
+    });
+    iframe.remove();
+    yield promiseIframeWindowGone;
+    cw = null;
+    ok(!iframe.contentWindow, "Managed to destroy iframe");
+
+    let someDir = "blah";
+    try {
+      someDir = yield new Promise((resolve, reject) => {
+        gDownloadLastDir.getFileAsync("http://www.mozilla.org/", function(dir) {
+          resolve(dir);
+        });
+      });
+    } catch (ex) {
+      ok(false, "Got an exception trying to get the directory where things should be saved.");
+      Cu.reportError(ex);
+    }
+    // NB: someDir can legitimately be null here when set, hence the 'blah' workaround:
+    isnot(someDir, "blah", "Should get a file even after the window was destroyed.");
+
+    try {
+      gDownloadLastDir.setFile("http://www.mozilla.org/", null);
+    } catch (ex) {
+      ok(false, "Got an exception trying to set the directory where things should be saved.");
+      Cu.reportError(ex);
+    }
+
+    yield promiseWindowClosed(win);
+    Services.prefs.clearUserPref(SAVE_PER_SITE_PREF);
+  };
+}
+
+add_task(test_deleted_iframe(false));
+add_task(test_deleted_iframe(false));
+add_task(test_deleted_iframe(true, {private: true}));
+add_task(test_deleted_iframe(true, {private: true}));
+
diff --git a/browser/components/downloads/test/browser/browser_indicatorDrop.js b/browser/components/downloads/test/browser/browser_indicatorDrop.js
new file mode 100644
index 000000000..368d85ccf
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_indicatorDrop.js
@@ -0,0 +1,67 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+XPCOMUtils.defineLazyModuleGetter(this, "HttpServer",
+  "resource://testing-common/httpd.js");
+
+registerCleanupFunction(function*() {
+  yield task_resetState();
+  yield task_clearHistory();
+});
+
+add_task(function* test_indicatorDrop() {
+  let downloadButton = document.getElementById("downloads-button");
+  ok(downloadButton, "download button present");
+
+  let scriptLoader = Cc["@mozilla.org/moz/jssubscript-loader;1"].
+      getService(Ci.mozIJSSubScriptLoader);
+  let EventUtils = {};
+  scriptLoader.loadSubScript("chrome://mochikit/content/tests/SimpleTest/EventUtils.js", EventUtils);
+
+  function* task_drop(urls) {
+    let dragData = [[{type: "text/plain", data: urls.join("\n")}]];
+
+    let list = yield Downloads.getList(Downloads.ALL);
+
+    let added = new Set();
+    let succeeded = new Set();
+    yield new Promise(function(resolve) {
+      let view = {
+        onDownloadAdded: function(download) {
+          added.add(download.source.url);
+        },
+        onDownloadChanged: function(download) {
+          if (!added.has(download.source.url))
+            return;
+          if (!download.succeeded)
+            return;
+          succeeded.add(download.source.url);
+          if (succeeded.size == urls.length) {
+            list.removeView(view).then(resolve);
+          }
+        }
+      };
+      list.addView(view).then(function() {
+        EventUtils.synthesizeDrop(downloadButton, downloadButton, dragData, "link", window);
+      });
+    });
+
+    for (let url of urls) {
+      ok(added.has(url), url + " is added to download");
+    }
+  }
+
+  // Ensure that state is reset in case previous tests didn't finish.
+  yield task_resetState();
+
+  yield setDownloadDir();
+
+  startServer();
+
+  yield* task_drop([httpUrl("file1.txt")]);
+  yield* task_drop([httpUrl("file1.txt"),
+                    httpUrl("file2.txt"),
+                    httpUrl("file3.txt")]);
+});
diff --git a/browser/components/downloads/test/browser/browser_libraryDrop.js b/browser/components/downloads/test/browser/browser_libraryDrop.js
new file mode 100644
index 000000000..fa7df8a87
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_libraryDrop.js
@@ -0,0 +1,72 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+XPCOMUtils.defineLazyModuleGetter(this, "HttpServer",
+  "resource://testing-common/httpd.js");
+
+registerCleanupFunction(function*() {
+  yield task_resetState();
+  yield task_clearHistory();
+});
+
+add_task(function* test_indicatorDrop() {
+  let scriptLoader = Cc["@mozilla.org/moz/jssubscript-loader;1"].
+      getService(Ci.mozIJSSubScriptLoader);
+  let EventUtils = {};
+  scriptLoader.loadSubScript("chrome://mochikit/content/tests/SimpleTest/EventUtils.js", EventUtils);
+
+  function task_drop(win, urls) {
+    let dragData = [[{type: "text/plain", data: urls.join("\n")}]];
+
+    let listBox = win.document.getElementById("downloadsRichListBox");
+    ok(listBox, "download list box present");
+
+    let list = yield Downloads.getList(Downloads.ALL);
+
+    let added = new Set();
+    let succeeded = new Set();
+    yield new Promise(function(resolve) {
+      let view = {
+        onDownloadAdded: function(download) {
+          added.add(download.source.url);
+        },
+        onDownloadChanged: function(download) {
+          if (!added.has(download.source.url))
+            return;
+          if (!download.succeeded)
+            return;
+          succeeded.add(download.source.url);
+          if (succeeded.size == urls.length) {
+            list.removeView(view).then(resolve);
+          }
+        }
+      };
+      list.addView(view).then(function() {
+        EventUtils.synthesizeDrop(listBox, listBox, dragData, "link", win);
+      });
+    });
+
+    for (let url of urls) {
+      ok(added.has(url), url + " is added to download");
+    }
+  }
+
+  // Ensure that state is reset in case previous tests didn't finish.
+  yield task_resetState();
+
+  setDownloadDir();
+
+  startServer();
+
+  let win = yield openLibrary("Downloads");
+  registerCleanupFunction(function() {
+    win.close();
+  });
+
+  yield* task_drop(win, [httpUrl("file1.txt")]);
+  yield* task_drop(win, [httpUrl("file1.txt"),
+                         httpUrl("file2.txt"),
+                         httpUrl("file3.txt")]);
+});
diff --git a/browser/components/downloads/test/browser/browser_overflow_anchor.js b/browser/components/downloads/test/browser/browser_overflow_anchor.js
new file mode 100644
index 000000000..a293a81cf
--- /dev/null
+++ b/browser/components/downloads/test/browser/browser_overflow_anchor.js
@@ -0,0 +1,115 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+registerCleanupFunction(function*() {
+  // Clean up when the test finishes.
+  yield task_resetState();
+});
+
+/**
+ * Make sure the downloads button and indicator overflows into the nav-bar
+ * chevron properly, and then when those buttons are clicked in the overflow
+ * panel that the downloads panel anchors to the chevron.
+ */
+add_task(function* test_overflow_anchor() {
+  // Ensure that state is reset in case previous tests didn't finish.
+  yield task_resetState();
+
+  // Record the original width of the window so we can put it back when
+  // this test finishes.
+  let oldWidth = window.outerWidth;
+
+  // The downloads button should not be overflowed to begin with.
+  let button = CustomizableUI.getWidget("downloads-button")
+                             .forWindow(window);
+  ok(!button.overflowed, "Downloads button should not be overflowed.");
+
+  // Hack - we lock the size of the default flex-y items in the nav-bar,
+  // namely, the URL and search inputs. That way we can resize the
+  // window without worrying about them flexing.
+  const kFlexyItems = ["urlbar-container", "search-container"];
+  registerCleanupFunction(() => unlockWidth(kFlexyItems));
+  lockWidth(kFlexyItems);
+
+  // Resize the window to half of its original size. That should
+  // be enough to overflow the downloads button.
+  window.resizeTo(oldWidth / 2, window.outerHeight);
+  yield waitForOverflowed(button, true);
+
+  let promise = promisePanelOpened();
+  button.node.doCommand();
+  yield promise;
+
+  let panel = DownloadsPanel.panel;
+  let chevron = document.getElementById("nav-bar-overflow-button");
+  is(panel.anchorNode, chevron, "Panel should be anchored to the chevron.");
+
+  DownloadsPanel.hidePanel();
+
+  // Unlock the widths on the flex-y items.
+  unlockWidth(kFlexyItems);
+
+  // Put the window back to its original dimensions.
+  window.resizeTo(oldWidth, window.outerHeight);
+
+  // The downloads button should eventually be un-overflowed.
+  yield waitForOverflowed(button, false);
+
+  // Now try opening the panel again.
+  promise = promisePanelOpened();
+  button.node.doCommand();
+  yield promise;
+
+  is(panel.anchorNode.id, "downloads-indicator-anchor");
+
+  DownloadsPanel.hidePanel();
+});
+
+/**
+ * For some node IDs, finds the nodes and sets their min-width's to their
+ * current width, preventing them from flex-shrinking.
+ *
+ * @param aItemIDs an array of item IDs to set min-width on.
+ */
+function lockWidth(aItemIDs) {
+  for (let itemID of aItemIDs) {
+    let item = document.getElementById(itemID);
+    let curWidth = item.getBoundingClientRect().width + "px";
+    item.style.minWidth = curWidth;
+  }
+}
+
+/**
+ * Clears the min-width's set on a set of IDs by lockWidth.
+ *
+ * @param aItemIDs an array of ItemIDs to remove min-width on.
+ */
+function unlockWidth(aItemIDs) {
+  for (let itemID of aItemIDs) {
+    let item = document.getElementById(itemID);
+    item.style.minWidth = "";
+  }
+}
+
+/**
+ * Waits for a node to enter or exit the overflowed state.
+ *
+ * @param aItem the node to wait for.
+ * @param aIsOverflowed if we're waiting for the item to be overflowed.
+ */
+function waitForOverflowed(aItem, aIsOverflowed) {
+  let deferOverflow = Promise.defer();
+  if (aItem.overflowed == aIsOverflowed) {
+    return deferOverflow.resolve();
+  }
+
+  let observer = new MutationObserver(function(aMutations) {
+    if (aItem.overflowed == aIsOverflowed) {
+      observer.disconnect();
+      deferOverflow.resolve();
+    }
+  });
+  observer.observe(aItem.node, {attributes: true});
+
+  return deferOverflow.promise;
+}
diff --git a/browser/components/downloads/test/browser/head.js b/browser/components/downloads/test/browser/head.js
new file mode 100644
index 000000000..bcf703eb6
--- /dev/null
+++ b/browser/components/downloads/test/browser/head.js
@@ -0,0 +1,300 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Provides infrastructure for automated download components tests.
+ */
+
+////////////////////////////////////////////////////////////////////////////////
+//// Globals
+
+XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
+                                  "resource://gre/modules/Downloads.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadsCommon",
+                                  "resource:///modules/DownloadsCommon.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+                                  "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
+                                  "resource://gre/modules/PlacesUtils.jsm");
+const nsIDM = Ci.nsIDownloadManager;
+
+var gTestTargetFile = FileUtils.getFile("TmpD", ["dm-ui-test.file"]);
+gTestTargetFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, FileUtils.PERMS_FILE);
+
+// Load mocking/stubbing library, sinon
+// docs: http://sinonjs.org/docs/
+Services.scriptloader.loadSubScript("resource://testing-common/sinon-1.16.1.js");
+
+registerCleanupFunction(function () {
+  gTestTargetFile.remove(false);
+
+  delete window.sinon;
+  delete window.setImmediate;
+  delete window.clearImmediate;
+});
+
+////////////////////////////////////////////////////////////////////////////////
+//// Asynchronous support subroutines
+
+function promiseOpenAndLoadWindow(aOptions)
+{
+  return new Promise((resolve, reject) => {
+    let win = OpenBrowserWindow(aOptions);
+    win.addEventListener("load", function onLoad() {
+      win.removeEventListener("load", onLoad);
+      resolve(win);
+    });
+  });
+}
+
+/**
+ * Waits for a load (or custom) event to finish in a given tab. If provided
+ * load an uri into the tab.
+ *
+ * @param tab
+ *        The tab to load into.
+ * @param [optional] url
+ *        The url to load, or the current url.
+ * @param [optional] event
+ *        The load event type to wait for.  Defaults to "load".
+ * @return {Promise} resolved when the event is handled.
+ * @resolves to the received event
+ * @rejects if a valid load event is not received within a meaningful interval
+ */
+function promiseTabLoadEvent(tab, url, eventType="load")
+{
+  let deferred = Promise.defer();
+  info("Wait tab event: " + eventType);
+
+  function handle(event) {
+    if (event.originalTarget != tab.linkedBrowser.contentDocument ||
+        event.target.location.href == "about:blank" ||
+        (url && event.target.location.href != url)) {
+      info("Skipping spurious '" + eventType + "'' event" +
+           " for " + event.target.location.href);
+      return;
+    }
+    // Remove reference to tab from the cleanup function:
+    realCleanup = () => {};
+    tab.linkedBrowser.removeEventListener(eventType, handle, true);
+    info("Tab event received: " + eventType);
+    deferred.resolve(event);
+  }
+
+  // Juggle a bit to avoid leaks:
+  let realCleanup = () => tab.linkedBrowser.removeEventListener(eventType, handle, true);
+  registerCleanupFunction(() => realCleanup());
+
+  tab.linkedBrowser.addEventListener(eventType, handle, true, true);
+  if (url)
+    tab.linkedBrowser.loadURI(url);
+  return deferred.promise;
+}
+
+function promiseWindowClosed(win)
+{
+  let promise = new Promise((resolve, reject) => {
+    Services.obs.addObserver(function obs(subject, topic) {
+      if (subject == win) {
+        Services.obs.removeObserver(obs, topic);
+        resolve();
+      }
+    }, "domwindowclosed", false);
+  });
+  win.close();
+  return promise;
+}
+
+
+function promiseFocus()
+{
+  let deferred = Promise.defer();
+  waitForFocus(deferred.resolve);
+  return deferred.promise;
+}
+
+function promisePanelOpened()
+{
+  let deferred = Promise.defer();
+
+  if (DownloadsPanel.panel && DownloadsPanel.panel.state == "open") {
+    return deferred.resolve();
+  }
+
+  // Hook to wait until the panel is shown.
+  let originalOnPopupShown = DownloadsPanel.onPopupShown;
+  DownloadsPanel.onPopupShown = function () {
+    DownloadsPanel.onPopupShown = originalOnPopupShown;
+    originalOnPopupShown.apply(this, arguments);
+
+    // Defer to the next tick of the event loop so that we don't continue
+    // processing during the DOM event handler itself.
+    setTimeout(deferred.resolve, 0);
+  };
+
+  return deferred.promise;
+}
+
+function* task_resetState()
+{
+  // Remove all downloads.
+  let publicList = yield Downloads.getList(Downloads.PUBLIC);
+  let downloads = yield publicList.getAll();
+  for (let download of downloads) {
+    publicList.remove(download);
+    yield download.finalize(true);
+  }
+
+  DownloadsPanel.hidePanel();
+
+  yield promiseFocus();
+}
+
+function* task_addDownloads(aItems)
+{
+  let startTimeMs = Date.now();
+
+  let publicList = yield Downloads.getList(Downloads.PUBLIC);
+  for (let item of aItems) {
+    let download = {
+      source: {
+        url: "http://www.example.com/test-download.txt",
+      },
+      target: {
+        path: gTestTargetFile.path,
+      },
+      succeeded: item.state == nsIDM.DOWNLOAD_FINISHED,
+      canceled: item.state == nsIDM.DOWNLOAD_CANCELED ||
+                item.state == nsIDM.DOWNLOAD_PAUSED,
+      error: item.state == nsIDM.DOWNLOAD_FAILED ? new Error("Failed.") : null,
+      hasPartialData: item.state == nsIDM.DOWNLOAD_PAUSED,
+      hasBlockedData: item.hasBlockedData || false,
+      startTime: new Date(startTimeMs++),
+    };
+    // `"errorObj" in download` must be false when there's no error.
+    if (item.errorObj) {
+      download.errorObj = item.errorObj;
+    }
+    yield publicList.add(yield Downloads.createDownload(download));
+  }
+}
+
+function* task_openPanel()
+{
+  yield promiseFocus();
+
+  let promise = promisePanelOpened();
+  DownloadsPanel.showPanel();
+  yield promise;
+}
+
+function* setDownloadDir() {
+  let tmpDir = Services.dirsvc.get("TmpD", Ci.nsIFile);
+  tmpDir.append("testsavedir");
+  if (!tmpDir.exists()) {
+    tmpDir.create(Ci.nsIFile.DIRECTORY_TYPE, 0o755);
+    registerCleanupFunction(function () {
+      try {
+        tmpDir.remove(true);
+      } catch (e) {
+        // On Windows debug build this may fail.
+      }
+    });
+  }
+
+  yield new Promise(resolve => {
+    SpecialPowers.pushPrefEnv({"set": [
+      ["browser.download.folderList", 2],
+      ["browser.download.dir", tmpDir, Ci.nsIFile],
+    ]}, resolve);
+  });
+}
+
+
+let gHttpServer = null;
+function startServer() {
+  gHttpServer = new HttpServer();
+  gHttpServer.start(-1);
+  registerCleanupFunction(function*() {
+     yield new Promise(function(resolve) {
+      gHttpServer.stop(resolve);
+    });
+  });
+
+  gHttpServer.registerPathHandler("/file1.txt", (request, response) => {
+    response.setStatusLine(null, 200, "OK");
+    response.write("file1");
+    response.processAsync();
+    response.finish();
+  });
+  gHttpServer.registerPathHandler("/file2.txt", (request, response) => {
+    response.setStatusLine(null, 200, "OK");
+    response.write("file2");
+    response.processAsync();
+    response.finish();
+  });
+  gHttpServer.registerPathHandler("/file3.txt", (request, response) => {
+    response.setStatusLine(null, 200, "OK");
+    response.write("file3");
+    response.processAsync();
+    response.finish();
+  });
+}
+
+function httpUrl(aFileName) {
+  return "http://localhost:" + gHttpServer.identity.primaryPort + "/" +
+    aFileName;
+}
+
+function task_clearHistory() {
+  return new Promise(function(resolve) {
+    Services.obs.addObserver(function observeCH(aSubject, aTopic, aData) {
+      Services.obs.removeObserver(observeCH, PlacesUtils.TOPIC_EXPIRATION_FINISHED);
+      resolve();
+    }, PlacesUtils.TOPIC_EXPIRATION_FINISHED, false);
+    PlacesUtils.history.clear();
+  });
+}
+
+function openLibrary(aLeftPaneRoot) {
+  let library = window.openDialog("chrome://browser/content/places/places.xul",
+                                  "", "chrome,toolbar=yes,dialog=no,resizable",
+                                  aLeftPaneRoot);
+
+  return new Promise(resolve => {
+    waitForFocus(resolve, library);
+  });
+}
+
+function promiseAlertDialogOpen(buttonAction) {
+  return new Promise(resolve => {
+    Services.ww.registerNotification(function onOpen(subj, topic, data) {
+      if (topic == "domwindowopened" && subj instanceof Ci.nsIDOMWindow) {
+        // The test listens for the "load" event which guarantees that the alert
+        // class has already been added (it is added when "DOMContentLoaded" is
+        // fired).
+        subj.addEventListener("load", function onLoad() {
+          subj.removeEventListener("load", onLoad);
+          if (subj.document.documentURI ==
+              "chrome://global/content/commonDialog.xul") {
+            Services.ww.unregisterNotification(onOpen);
+
+            let dialog = subj.document.getElementById("commonDialog");
+            ok(dialog.classList.contains("alert-dialog"),
+               "The dialog element should contain an alert class.");
+
+            let doc = subj.document.documentElement;
+            doc.getButton(buttonAction).click();
+            resolve();
+          }
+        });
+      }
+    });
+  });
+}
diff --git a/browser/components/downloads/test/unit/.eslintrc.js b/browser/components/downloads/test/unit/.eslintrc.js
new file mode 100644
index 000000000..d35787cd2
--- /dev/null
+++ b/browser/components/downloads/test/unit/.eslintrc.js
@@ -0,0 +1,7 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "../../../../../testing/xpcshell/xpcshell.eslintrc.js"
+  ]
+};
diff --git a/browser/components/downloads/test/unit/head.js b/browser/components/downloads/test/unit/head.js
new file mode 100644
index 000000000..d7ce4d48a
--- /dev/null
+++ b/browser/components/downloads/test/unit/head.js
@@ -0,0 +1,18 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Provides infrastructure for automated download components tests.
+ */
+
+////////////////////////////////////////////////////////////////////////////////
+//// Globals
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cu = Components.utils;
+var Cr = Components.results;
+
+Cu.import("resource:///modules/DownloadsCommon.jsm");
diff --git a/browser/components/downloads/test/unit/test_DownloadsCommon.js b/browser/components/downloads/test/unit/test_DownloadsCommon.js
new file mode 100644
index 000000000..46afbaef9
--- /dev/null
+++ b/browser/components/downloads/test/unit/test_DownloadsCommon.js
@@ -0,0 +1,37 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Tests for the functions located directly in the "DownloadsCommon" object.
+ */
+
+function testFormatTimeLeft(aSeconds, aExpectedValue, aExpectedUnitString)
+{
+  let expected = "";
+  if (aExpectedValue) {
+    // Format the expected result based on the current language.
+    expected = DownloadsCommon.strings[aExpectedUnitString](aExpectedValue);
+  }
+  do_check_eq(DownloadsCommon.formatTimeLeft(aSeconds), expected);
+}
+
+function run_test()
+{
+  testFormatTimeLeft(      0,   "", "");
+  testFormatTimeLeft(      1,  "1", "shortTimeLeftSeconds");
+  testFormatTimeLeft(     29, "29", "shortTimeLeftSeconds");
+  testFormatTimeLeft(     30, "30", "shortTimeLeftSeconds");
+  testFormatTimeLeft(     31,  "1", "shortTimeLeftMinutes");
+  testFormatTimeLeft(     60,  "1", "shortTimeLeftMinutes");
+  testFormatTimeLeft(     89,  "1", "shortTimeLeftMinutes");
+  testFormatTimeLeft(     90,  "2", "shortTimeLeftMinutes");
+  testFormatTimeLeft(     91,  "2", "shortTimeLeftMinutes");
+  testFormatTimeLeft(   3600,  "1", "shortTimeLeftHours");
+  testFormatTimeLeft(  86400, "24", "shortTimeLeftHours");
+  testFormatTimeLeft( 169200, "47", "shortTimeLeftHours");
+  testFormatTimeLeft( 172800,  "2", "shortTimeLeftDays");
+  testFormatTimeLeft(8553600, "99", "shortTimeLeftDays");
+  testFormatTimeLeft(8640000, "99", "shortTimeLeftDays");
+}
diff --git a/browser/components/downloads/test/unit/xpcshell.ini b/browser/components/downloads/test/unit/xpcshell.ini
new file mode 100644
index 000000000..f53a8cf89
--- /dev/null
+++ b/browser/components/downloads/test/unit/xpcshell.ini
@@ -0,0 +1,7 @@
+[DEFAULT]
+head = head.js
+tail =
+firefox-appdir = browser
+skip-if = toolkit == 'android'
+
+[test_DownloadsCommon.js]