Revert of [serializer] print use count of external references.

src/flag-definitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines all of the flags.  It is separated into different section,
 // for Debug, Release, Logging and Profiling, etc.  To add a new flag, find the
 // correct section, and use one of the DEFINE_ macros, without a trailing ';'.
 //
 // This include does not have a guard, because it is a template-style include,
 // which can be included multiple times in different modes.  It expects to have
@@ skipping 609 matching lines @@
 DEFINE_BOOL(always_osr, false, "always try to OSR functions")
 DEFINE_BOOL(prepare_always_opt, false, "prepare for turning on always opt")
 DEFINE_BOOL(trace_deopt, false, "trace optimize function deoptimization")
 DEFINE_BOOL(trace_stub_failures, false,
             "trace deoptimization of generated code stubs")
 
 DEFINE_BOOL(serialize_toplevel, true, "enable caching of toplevel scripts")
 DEFINE_BOOL(serialize_eager, false, "compile eagerly when caching scripts")
 DEFINE_BOOL(serialize_age_code, false, "pre age code in the code cache")
 DEFINE_BOOL(trace_serializer, false, "print code serializer trace")
-#ifdef DEBUG
-DEFINE_BOOL(external_reference_stats, false,
-            "print statistics on external references used during serialization")
-#endif  // DEBUG
 
 // compiler.cc
 DEFINE_INT(min_preparse_length, 1024,
            "minimum length for automatic enable preparsing")
 DEFINE_INT(max_opt_count, 10,
            "maximum number of optimization attempts before giving up.")
 
 // compilation-cache.cc
 DEFINE_BOOL(compilation_cache, true, "enable compilation cache")
 
@@ skipping 583 matching lines @@
 #undef DEFINE_ALIAS_FLOAT
 #undef DEFINE_ALIAS_ARGS
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS
 
 #undef COMMA