Prevent repeat loads of js/css, fix xul loading

- don't run if xml has already run (by setting global variable)
- ignore script cache (so that changes to scripts can show up on restart or new windows without removing cache).
- don't load already registered css (for new windows)
- fix loading of xul files by increasing delay (previously only the first xul file gets loaded)

userChrome.xml

@@ -9,6 +9,9 @@ https://opensource.org/licenses/MIT
     <binding id="js" extends="chrome://global/content/bindings/toolbarbutton.xml#menu">
         <implementation>
             <constructor><![CDATA[
+                if(window.userChromeJsMod) return;
+                window.userChromeJsMod = true;
+                
                 var chromeFiles = FileUtils.getDir("UChrm", []).directoryEntries;
                 var xulFiles = [];
                 var sss = Cc['@mozilla.org/content/style-sheet-service;1'].getService(Ci.nsIStyleSheetService);
@@ -19,24 +22,26 @@ https://opensource.org/licenses/MIT
                     
                     if(file.isFile()) {
                         if(/(^userChrome|\.uc)\.js$/i.test(file.leafName)) {
-                            Services.scriptloader.loadSubScript(fileURI.spec, window);
+                            Services.scriptloader.loadSubScriptWithOptions(fileURI.spec, {target: window, ignoreCache: true});
                         }
                         else if(/(^userChrome|\.uc)\.xul$/i.test(file.leafName)) {
                             xulFiles.push(fileURI.spec);
                         }
                         else if(/\.as\.css$/i.test(file.leafName)) {
-                            sss.loadAndRegisterSheet(fileURI, sss.AGENT_SHEET);
+                            if(!sss.sheetRegistered(fileURI, sss.AGENT_SHEET))
+                                sss.loadAndRegisterSheet(fileURI, sss.AGENT_SHEET);
                         }
                         else if(/^(?!(userChrome|userContent)\.css$).+\.css$/i.test(file.leafName)) {
-                            sss.loadAndRegisterSheet(fileURI, sss.USER_SHEET);
+                            if(!sss.sheetRegistered(fileURI, sss.USER_SHEET))
+                                sss.loadAndRegisterSheet(fileURI, sss.USER_SHEET);
                         }
                     }
                 }
                 
                 setTimeout(function loadXUL() {
                     if(xulFiles.length > 0) {
                         document.loadOverlay(xulFiles.shift(), null);
-                        setTimeout(loadXUL, 0);
+                        setTimeout(loadXUL, 5);
                     }
                 }, 0);
             ]]></constructor>