Firefox: increase item count in built-in download panel(browser.download.useToolkitUI = false)

increaseDownloadCount.js

// https://gist.github.com/Infocatcher/5387328
// More: https://github.com/Infocatcher/Download_Panel_Tweaker
// (c) Infocatcher 2013, 2015

var itemCountLimit = 5;
// resource://app/modules/DownloadsCommon.jsm, see getSummary() function
if(DownloadsCommon._privateSummary)
	DownloadsCommon._privateSummary._numToExclude = itemCountLimit;
if(DownloadsCommon._summary)
	DownloadsCommon._summary._numToExclude = itemCountLimit;
// chrome://browser/content/downloads/downloads.js
DownloadsView.kItemCountLimit = itemCountLimit;
if(DownloadsPanel._state != DownloadsPanel.kStateUninitialized) {
	if("onDataInvalidated" in DownloadsView)
		DownloadsView.onDataInvalidated(); // This calls DownloadsPanel.terminate();
	else { // Firefox 28+
		// Based on code from chrome://browser/content/downloads/downloads.js in Firefox 25
		DownloadsPanel.terminate();
		DownloadsView.richListBox.textContent = "";
		if("_downloads" in DownloadsView) // Firefox 38+
			DownloadsView._downloads = [];
		else {
			DownloadsView._viewItems = {};
			DownloadsView._dataItems = [];
		}
	}
	DownloadsPanel.initialize(function() {});
}