More changes to use #ifndef PRODUCT ... #endif explicitly instead of relying on compiler magic.

runtime/vm/metrics.h

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_METRICS_H_
 #define VM_METRICS_H_
 
 #include "vm/allocation.h"
 
 namespace dart {
@@ skipping 38 matching lines @@
             const char* description,
             Unit unit);
 
   // Initialize and register a metric for the VM.
   void Init(const char* name,
             const char* description,
             Unit unit);
 
   virtual ~Metric();
 
+#ifndef PRODUCT
   void PrintJSON(JSONStream* stream);
+#endif  // !PRODUCT
 
   // Returns a zone allocated string.
   static char* ValueToString(int64_t value, Unit unit);
 
   // Returns a zone allocated string.
   char* ToString();
 
   int64_t value() const { return value_; }
   void set_value(int64_t value) { value_ = value; }
 
@@ skipping 101 matching lines @@
 
 
 class MetricHeapUsed : public Metric {
  protected:
   virtual int64_t Value() const;
 };
 
 }  // namespace dart
 
 #endif  // VM_METRICS_H_