Fix issue 2888.

vm/unit_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 <stdio.h>
 
 #include "vm/unit_test.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
@@ skipping 89 matching lines @@
   }
   return result;
 }
 
 
 Dart_Handle TestCase::LoadTestScript(const char* script,
                                      Dart_NativeEntryResolver resolver,
                                      Dart_Handle import_map) {
   Dart_Handle url = Dart_NewString(TestCase::url());
   Dart_Handle source = Dart_NewString(script);
-  Dart_Handle lib = Dart_LoadScript(url, source, LibraryTagHandler, import_map);
+  Dart_Handle result = Dart_SetLibraryTagHandler(LibraryTagHandler);
+  EXPECT_VALID(result);
+  Dart_Handle lib = Dart_LoadScript(url, source, import_map);
   DART_CHECK_VALID(lib);
-  Dart_Handle result = Dart_SetNativeResolver(lib, resolver);
+  result = Dart_SetNativeResolver(lib, resolver);
   DART_CHECK_VALID(result);
   return lib;
 }
 
 
 Dart_Handle TestCase::lib() {
   Dart_Handle url = Dart_NewString(TestCase::url());
   Dart_Handle lib = Dart_LookupLibrary(url);
   DART_CHECK_VALID(lib);
   ASSERT(Dart_IsLibrary(lib));
@@ skipping 98 matching lines @@
 
 bool CompilerTest::TestCompileFunction(const Function& function) {
   Isolate* isolate = Isolate::Current();
   ASSERT(isolate != NULL);
   ASSERT(ClassFinalizer::AllClassesFinalized());
   const Error& error = Error::Handle(Compiler::CompileFunction(function));
   return error.IsNull();
 }
 
 }  // namespace dart