Fix performance of array literals (e.g. "[1, 2]"). Improves speed of DeltaBlue.

runtime/lib/array_patch.dart

Index: runtime/lib/array_patch.dart
===================================================================
--- runtime/lib/array_patch.dart	(revision 16982)
+++ runtime/lib/array_patch.dart	(working copy)
@@ -45,12 +45,12 @@
   // Factory constructing a mutable List from a parser generated List literal.
   // [elements] contains elements that are already type checked.
   factory List._fromLiteral(List elements) {
-    var list = new List<E>();
-    if (elements.length > 0) {
-      list._setData(elements);
-      list.length = elements.length;
+    if (elements.isEmpty) {
+      return new _GrowableObjectArray<E>(0);
     }
-    return list;
+    var result = new _GrowableObjectArray<E>.withData(elements);
+    result._setLength(elements.length);
+    return result;
   }
 
   static void _throwArgumentError(int length) {