Test again the library url in the error message shortened in r3965.

runtime/vm/dart_api_impl_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_api_state.h"
 #include "vm/thread.h"
@@ skipping 1477 matching lines @@
 
   // Invoke a function which returns an object of type NativeFields.
   result = Dart_InvokeStatic(lib,
                              Dart_NewString("NativeFieldsTest"),
                              Dart_NewString("testMain"),
                              0,
                              NULL);
   // We expect the test script to fail finalization with the error below:
   EXPECT(Dart_IsError(result));
   Dart_Handle expected_error = Dart_Error(
-      "'dart:test-lib': Error: line 1 pos 38: class 'NativeFields' is trying");
+      "'dart:test-lib': Error: line 1 pos 38: "
+      "class 'NativeFields' is trying to extend a native fields class, "
+      "but library '%s' has no native resolvers",
+      TestCase::url());
   EXPECT_SUBSTRING(Dart_GetError(expected_error), Dart_GetError(result));
 }
 
 
 static void TestNativeFields(Dart_Handle retobj) {
   // Access and set various instance fields of the object.
   Dart_Handle result = Dart_GetInstanceField(retobj, Dart_NewString("fld3"));
   EXPECT(Dart_IsError(result));
   result = Dart_GetInstanceField(retobj, Dart_NewString("fld0"));
   EXPECT_VALID(result);
@@ skipping 1712 matching lines @@
   // We should have received the expected number of interrupts.
   EXPECT_EQ(kInterruptCount, interrupt_count);
 
   // Give the spawned thread enough time to properly exit.
   Isolate::SetInterruptCallback(saved);
 }
 
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64).
 
 }  // namespace dart