Add an API for enumerating persistent handles

src/global-handles.cc

Index: src/global-handles.cc
diff --git a/src/global-handles.cc b/src/global-handles.cc
index 9c0ad45179dc538bc39aab0c08036dca229677b4..c09ba4b476b97e8fc524bc4180c8017d72814167 100644
--- a/src/global-handles.cc
+++ b/src/global-handles.cc
@@ -448,6 +448,11 @@ void GlobalHandles::MarkIndependent(Object** location) {
 }
 
 
+bool GlobalHandles::IsIndependent(Object** location) {
+  return Node::FromLocation(location)->is_independent();
+}
+
+
 bool GlobalHandles::IsNearDeath(Object** location) {
   return Node::FromLocation(location)->IsNearDeath();
 }
@@ -462,6 +467,9 @@ void GlobalHandles::SetWrapperClassId(Object** location, uint16_t class_id) {
   Node::FromLocation(location)->set_wrapper_class_id(class_id);
 }
 
+uint16_t GlobalHandles::GetWrapperClassId(Object** location) {
+  return Node::FromLocation(location)->wrapper_class_id();
+}
 
 void GlobalHandles::IterateWeakRoots(ObjectVisitor* v) {
   for (NodeIterator it(this); !it.done(); it.Advance()) {