Remove multiple GC calls and replace GCController.collect calls with GCController.collectAll

LayoutTests/fast/dom/resources/script-element-gc.js

 function gc()
 {
     if (window.GCController)
-        return GCController.collect();
+        return GCController.collectAll();
 
     for (var i = 0; i < 10000; i++) { // > force garbage collection (FF requires about 9K allocations before a collect)
         var s = new String("");
     }
 }
 
 function removeScriptElement() {
     var s = document.getElementById('theScript');
     s.parentNode.removeChild(s);
 }
 
 removeScriptElement();
 gc();