Implement automatic loading of dart:core_native_fields library

bin/dartutils.cc

Index: bin/dartutils.cc
===================================================================
--- bin/dartutils.cc	(revision 1520)
+++ bin/dartutils.cc	(working copy)
@@ -4,11 +4,13 @@
 
 #include "bin/dartutils.h"
 
-const char* DartUtils::kBuiltinLibURL = "./dart:builtin-lib";
+const char* DartUtils::kBuiltinLibURL = "dart:builtin-lib";
+const char* DartUtils::kCoreLibURL = "dart:core";
+const char* DartUtils::kCoreImplLibURL = "dart:coreimpl";
+const char* DartUtils::kCoreNativeFieldsLibURL = "dart:core-native-fields";
 const char* DartUtils::kBuiltinLibSpec = "library { }";
 const char* DartUtils::kIdFieldName = "_id";
 
-
 int64_t DartUtils::GetIntegerValue(Dart_Handle value_obj) {
   ASSERT(Dart_IsInteger(value_obj));
   int64_t value = 0;