Enhanced options for various download commands

[Infocatcher]

We already track Tools:Downloads command and downloads hotkey here: #2, also we should additionally handle #downloadsHistory item ("Show All Downloads" button in download panel) for #6.
So we can detect 1) downloads command, 2) downloads hotkey and 3) "Show All Downloads" from download panel.
And it's easy to do something good instead of default actions.
And we can override opening of "about:downloads" tab for private windows as well.

[added at 2014-01-13] Support for Downloads Window extension: #16

For example (see resource://app/components/DownloadsUI.js), open old window

var toolkitUI = Components.classesByID["{7dfdf0d1-aff6-4a34-bad1-d0fe74601642}"]
    .getService(Components.interfaces.nsIDownloadManagerUI);
toolkitUI.show(window/*, aDownload, aReason, aUsePrivateUI*/);

or open downloads in tab

window.openUILinkIn("about:downloads", "tab");

or open Library

      let organizer = Services.wm.getMostRecentWindow("Places:Organizer");
      if (!organizer) {
        parentWindow.openDialog("chrome://browser/content/places/places.xul",
                                "", "chrome,toolbar=yes,dialog=no,resizable",
                                "Downloads");
      } else {
        organizer.PlacesOrganizer.selectLeftPaneQuery("Downloads");
        organizer.focus();
      }

[Infocatcher]

Oh, too many things for options page...

Downloads menu item                               [Open old downloads window  v]
Downloads menu item in private window             [Default (don't override)   v]
“Show All Downloads” item                         [Default (don't override)   v]
“Show All Downloads” item in private window       [Default (don't override)   v]
Hotkey for downloads (Ctrl+J)                     [Toggle download panel      v]
Hotkey for downloads (Ctrl+J) in private window   [Toggle download panel      v]

[Infocatcher]

Oh, too many things for options page...

Current appearance:

A but tricky (for margins) and Firefox itself is buggy width menulists:

[Infocatcher]

Also we have "Downloads" button on about:home page...

chrome://browser/content/browser.js

messageManager.loadFrameScript("chrome://browser/content/content.js", true);

chrome://browser/content/content.js

  onClick: function(aEvent) {
    ...
      case "downloads":
        sendAsyncMessage("AboutHome:Downloads");

resource:///components/nsBrowserGlue.js => resource:///modules/AboutHome.jsm

  MESSAGES: [
    ...
    "AboutHome:Downloads",
    ...
  ],

  init: function() {
    let mm = Cc["@mozilla.org/globalmessagemanager;1"].getService(Ci.nsIMessageListenerManager);

    for (let msg of this.MESSAGES) {
      mm.addMessageListener(msg, this);
    }

Anyway, seems that we can't use this way to handle "AboutHome:Downloads" message (missing things like event.preventDefault()/stopPropagation()):
https://developer.mozilla.org/en-US/docs/XPCOM_Interface_Reference/nsIFrameMessageManager
https://developer.mozilla.org/en-US/docs/XPCOM_Interface_Reference/nsIFrameMessageListener
But we still can handle "click" event before content script...