Fix compilation error with latest Xcode.

src/hydrogen-check-elimination.h

 // Copyright 2013 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 21 matching lines @@
 #include "hydrogen-alias-analysis.h"
 
 namespace v8 {
 namespace internal {
 
 
 // Remove CheckMaps instructions through flow- and branch-sensitive analysis.
 class HCheckEliminationPhase : public HPhase {
  public:
   explicit HCheckEliminationPhase(HGraph* graph)
-    : HPhase("H_Check Elimination", graph),
-      aliasing_(),
-      redundant_(0),
-      removed_(0),
-      removed_cho_(0),
-      narrowed_(0),
-      loads_(0),
-      empty_(0),
-      compares_true_(0),
-      compares_false_(0),
-      transitions_(0) { }
+      : HPhase("H_Check Elimination", graph), aliasing_() {
+#ifdef DEBUG
+    redundant_ = 0;
+    removed_ = 0;
+    removed_cho_ = 0;
+    narrowed_ = 0;
+    loads_ = 0;
+    empty_ = 0;
+    compares_true_ = 0;
+    compares_false_ = 0;
+    transitions_ = 0;
+#endif
+  }
 
   void Run();
 
   friend class HCheckTable;
 
  private:
   void PrintStats();
 
   HAliasAnalyzer* aliasing_;
+#ifdef DEBUG
   int redundant_;
   int removed_;
   int removed_cho_;
   int narrowed_;
   int loads_;
   int empty_;
   int compares_true_;
   int compares_false_;
   int transitions_;
+#endif
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_CHECK_ELIMINATION_H_