Use Object::null_instance and Object::null_function and do not create Handles everytime.

runtime/vm/bootstrap.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 "vm/bootstrap.h"
 
 #include "include/dart_api.h"
 
 #include "vm/bootstrap_natives.h"
 #include "vm/class_finalizer.h"
@@ skipping 136 matching lines @@
   if (update_lib_status) {
     library.SetLoadInProgress();
   }
   const Error& error = Error::Handle(Compiler::Compile(library, script));
   if (update_lib_status) {
     if (error.IsNull()) {
       library.SetLoaded();
     } else {
       // Compilation errors are not Dart instances, so just mark the library
       // as having failed to load without providing an error instance.
-      library.SetLoadError(Instance::Handle());
+      library.SetLoadError(Object::null_instance());
     }
   }
   return error.raw();
 }
 
 
 static Dart_Handle LoadPartSource(Isolate* isolate,
                                   const Library& lib,
                                   const String& uri) {
   const String& part_source = String::Handle(
@@ skipping 161 matching lines @@
     Compiler::CompileClass(cls);
   }
 
   // Restore the library tag handler for the isolate.
   isolate->set_library_tag_handler(saved_tag_handler);
 
   return error.raw();
 }
 
 }  // namespace dart