Add NativeEnqueuer to work with the Enqueuer.

sdk/lib/_internal/compiler/implementation/lib/string_helper.dart

Index: sdk/lib/_internal/compiler/implementation/lib/string_helper.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/string_helper.dart b/sdk/lib/_internal/compiler/implementation/lib/string_helper.dart
index f70a975ac6666af26e3ff84154b97c9ec51140d8..70580dfad7f5ecae00602a08299d741e7ff45a60 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/string_helper.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/string_helper.dart
@@ -124,10 +124,10 @@ stringReplaceFirstUnchecked(receiver, from, to) {
 
 stringSplitUnchecked(receiver, pattern) {
   if (pattern is String) {
-    return JS('List', r'#.split(#)', receiver, pattern);
+    return JS('=List', r'#.split(#)', receiver, pattern);
   } else if (pattern is JSSyntaxRegExp) {
     var re = regExpGetNative(pattern);
-    return JS('List', r'#.split(#)', receiver, re);
+    return JS('=List', r'#.split(#)', receiver, re);
   } else {
     throw "String.split(Pattern) UNIMPLEMENTED";
   }