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

LayoutTests/resources/gc.js

 // If there is no window.gc() already defined, define one using the best
 // method we can find.
 // The slow fallback should not hit in the actual test environment.
 if (!window.gc)
 {
     window.gc = function()
     {
         if (window.GCController)
-            return GCController.collect();
+            return GCController.collectAll();
         function gcRec(n) {
             if (n < 1)
                 return {};
             var temp = {i: "ab" + i + (i / 100000)};
             temp += "foo";
             gcRec(n-1);
         }
         for (var i = 0; i < 10000; i++)
             gcRec(10);
     }
 }