perf(orderBy): copy array with slice instead of for loop

Use array slice method to copy entire array instead of a for loop
http://jsperf.com/new-array-vs-splice-vs-slice/54

Closes #9942

src/ng/filter/orderBy.js

@@ -146,9 +146,7 @@ function orderByFilter($parse){
         return compare(get(a),get(b));
       }, descending);
     });
-    var arrayCopy = [];
-    for ( var i = 0; i < array.length; i++) { arrayCopy.push(array[i]); }
-    return arrayCopy.sort(reverseComparator(comparator, reverseOrder));
+    return slice.call(array).sort(reverseComparator(comparator, reverseOrder));
 
     function comparator(o1, o2){
       for ( var i = 0; i < sortPredicate.length; i++) {