Merge commit '50d3e596bbe89c95615f96eb71f6bc5be737a1db' into Basilisk-releasev2018.07.18

# Conflicts:
#	browser/app/profile/firefox.js
#	browser/components/preferences/jar.mn

1 files changed, 1732 insertions, 0 deletions

diff --git a/application/basilisk/components/downloads/content/downloads.js b/application/basilisk/components/downloads/content/downloads.js
new file mode 100644
index 000000000..57397c815
--- /dev/null
+++ b/application/basilisk/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);