Replace dart_core.js with actual compiled SDK

test/generated_sdk/lib/core/core.dart

Index: test/generated_sdk/lib/core/core.dart
diff --git a/test/generated_sdk/lib/core/core.dart b/test/generated_sdk/lib/core/core.dart
index 52ee5ffff6e6d4e01d89bb66e7ad95a15d3838f3..79fe783d7cbf315ba0d2c3ff0dab3b16e0a9aa32 100644
--- a/test/generated_sdk/lib/core/core.dart
+++ b/test/generated_sdk/lib/core/core.dart
@@ -201,6 +201,7 @@ import 'dart:_js_helper' show patch,
                               Primitives,
                               stringJoinUnchecked,
                               objectHashCode;
+import 'dart:_foreign_helper' show JS;
 
 String _symbolToString(Symbol symbol) => _symbol_dev.Symbol.getName(symbol);
 _symbolMapToStringMap(Map<Symbol, dynamic> map) {
@@ -211,6 +212,6 @@ _symbolMapToStringMap(Map<Symbol, dynamic> map) {
   });
   return result;
 }
-class _ListConstructorSentinel extends JSInt {
+class _ListConstructorSentinel {
   const _ListConstructorSentinel();
 }