Fix zone_allocator to support comparison

src/zone-allocator.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 51 matching lines @@
   }
   void deallocate(pointer p, size_type) { /* noop for Zones */ }
 
   size_type max_size() const throw() {
     size_type max = static_cast<size_type>(-1) / sizeof(T);
     return (max > 0 ? max : 1);
   }
   void construct(pointer p, const T& val) {
     new(static_cast<void*>(p)) T(val);
   }
-  void destroy(pointer p) { (static_cast<T*>(p))->~T(); }
+  void destroy(pointer p) { p->~T(); }
+
+  bool operator==(zone_allocator const& other) {
+    return zone_ == other.zone_;
+  }
+  bool operator!=(zone_allocator const& other) {
+    return zone_ != other.zone_;
+  }
 
  private:
   Zone* zone_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ZONE_ALLOCATOR_H_