Reverting 3174. Aka reapplying 3150, 3151 and 3159. Aka api accessor

src/handles.cc

Index: src/handles.cc
diff --git a/src/handles.cc b/src/handles.cc
index b764334e830881859fbce0823699b2a19337c1d8..275fe6a7c1228abc8e3351bf0a4e722e01f53475 100644
--- a/src/handles.cc
+++ b/src/handles.cc
@@ -105,6 +105,21 @@ void HandleScope::ZapRange(Object** start, Object** end) {
 }
 
 
+Address HandleScope::current_extensions_address() {
+  return reinterpret_cast<Address>(&current_.extensions);
+}
+
+
+Address HandleScope::current_next_address() {
+  return reinterpret_cast<Address>(&current_.next);
+}
+
+
+Address HandleScope::current_limit_address() {
+  return reinterpret_cast<Address>(&current_.limit);
+}
+
+
 Handle<FixedArray> AddKeysFromJSArray(Handle<FixedArray> content,
                                       Handle<JSArray> array) {
   CALL_HEAP_FUNCTION(content->AddKeysFromJSArray(*array), FixedArray);