Put zapping of local handles behind the extra checks flag.

src/api.h

 // Copyright 2012 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 554 matching lines @@
     internal::Object** block_start = blocks_.last();
     internal::Object** block_limit = block_start + kHandleBlockSize;
 #ifdef DEBUG
     // NoHandleAllocation may make the prev_limit to point inside the block.
     if (block_start <= prev_limit && prev_limit <= block_limit) break;
 #else
     if (prev_limit == block_limit) break;
 #endif
 
     blocks_.RemoveLast();
-#ifdef DEBUG
-    v8::ImplementationUtilities::ZapHandleRange(block_start, block_limit);
+#ifdef ENABLE_EXTRA_CHECKS
+    internal::HandleScope::ZapRange(block_start, block_limit);
 #endif
     if (spare_ != NULL) {
       DeleteArray(spare_);
     }
     spare_ = block_start;
   }
   ASSERT((blocks_.is_empty() && prev_limit == NULL) ||
          (!blocks_.is_empty() && prev_limit != NULL));
 }
 
 
 class Testing {
  public:
   static v8::Testing::StressType stress_type() { return stress_type_; }
   static void set_stress_type(v8::Testing::StressType stress_type) {
     stress_type_ = stress_type;
   }
 
  private:
   static v8::Testing::StressType stress_type_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_API_H_