Reduce the memory used by frame elements from two words to one by...

src/zone.h

Index: src/zone.h
===================================================================
--- src/zone.h	(revision 1947)
+++ src/zone.h	(working copy)
@@ -180,10 +180,15 @@
     nesting_++;
   }
 
-  ~ZoneScope() {
-    if (--nesting_ == 0 && mode_ == DELETE_ON_EXIT) Zone::DeleteAll();
+  virtual ~ZoneScope() {
+    if (ShouldDeleteOnExit()) Zone::DeleteAll();
+    --nesting_;
   }
 
+  bool ShouldDeleteOnExit() {
+    return nesting_ == 1 && mode_ == DELETE_ON_EXIT;
+  }
+
   // For ZoneScopes that do not delete on exit by default, call this
   // method to request deletion on exit.
   void DeleteOnExit() {