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

src/handles.h

Index: src/handles.h
diff --git a/src/handles.h b/src/handles.h
index 5d574657c5f0505346cd6fedb6f63bde1b8388c2..d3e9b788b5c6e8690a9885fd3cc0d08157d4a098 100644
--- a/src/handles.h
+++ b/src/handles.h
@@ -133,6 +133,13 @@ class HandleScope {
     return result;
   }
 
+  // Deallocates any extensions used by the current scope.
+  static void DeleteExtensions();
+
+  static Address current_extensions_address();
+  static Address current_next_address();
+  static Address current_limit_address();
+
  private:
   // Prevent heap allocation or illegal handle scopes.
   HandleScope(const HandleScope&);
@@ -166,9 +173,6 @@ class HandleScope {
   // Extend the handle scope making room for more handles.
   static internal::Object** Extend();
 
-  // Deallocates any extensions used by the current scope.
-  static void DeleteExtensions();
-
   // Zaps the handles in the half-open interval [start, end).
   static void ZapRange(internal::Object** start, internal::Object** end);