Rework service extensions to be safe

runtime/lib/developer.cc

 // Copyright (c) 2015, 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_natives.h"
 
 #include "include/dart_api.h"
 
 #include "vm/debugger.h"
 #include "vm/exceptions.h"
@@ skipping 41 matching lines @@
                         timestamp.AsInt64Value(),
                         level.Value(),
                         name,
                         message,
                         dart_zone,
                         error,
                         stack_trace);
   return Object::null();
 }
 
+
+DEFINE_NATIVE_ENTRY(Developer_lookupExtension, 1) {
+  GET_NON_NULL_NATIVE_ARGUMENT(String, name, arguments->NativeArgAt(0));
+  return isolate->LookupServiceExtensionHandler(name);
+}
+
+
+DEFINE_NATIVE_ENTRY(Developer_registerExtension, 2) {
+  GET_NON_NULL_NATIVE_ARGUMENT(String, name, arguments->NativeArgAt(0));
+  GET_NON_NULL_NATIVE_ARGUMENT(Instance, handler, arguments->NativeArgAt(1));
+  isolate->RegisterServiceExtensionHandler(name, handler);
+  return Object::null();
+}
+
 }  // namespace dart