Implement automatic loading of dart:core_native_fields library

vm/unit_test.cc

Index: vm/unit_test.cc
===================================================================
--- vm/unit_test.cc	(revision 1465)
+++ vm/unit_test.cc	(working copy)
@@ -48,11 +48,21 @@
 }
 
 
+static Dart_Handle LibraryTagHandler(Dart_LibraryTag tag,
+                                     Dart_Handle library,
+                                     Dart_Handle url) {
+  if (tag == kCanonicalizeUrl) {
+    return url;
+  }
+  return Dart_LookupLibrary(url);
+}
+
+
 Dart_Handle TestCase::LoadTestScript(const char* script,
                                      Dart_NativeEntryResolver resolver) {
   Dart_Handle url = Dart_NewString(TestCase::url());
   Dart_Handle source = Dart_NewString(script);
-  Dart_Handle lib = Dart_LoadScript(url, source, NULL);
+  Dart_Handle lib = Dart_LoadScript(url, source, LibraryTagHandler);
   ASSERT(Dart_IsValid(lib));
   Dart_Handle result = Dart_SetNativeResolver(lib, resolver);
   ASSERT(Dart_IsValid(result));