Activate code aging by default.

src/flag-definitions.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 386 matching lines @@
             "report fragmentation for old pointer and data pages")
 DEFINE_bool(trace_external_memory, false,
             "print amount of external allocated memory after each time "
             "it is adjusted.")
 DEFINE_bool(collect_maps, true,
             "garbage collect maps from which no objects can be reached")
 DEFINE_bool(flush_code, true,
             "flush code that we expect not to use again (during full gc)")
 DEFINE_bool(flush_code_incrementally, false,
             "flush code that we expect not to use again (incrementally)")
-DEFINE_bool(age_code, false,
+DEFINE_bool(age_code, true,
             "track un-executed functions to age code and flush only "
             "old code")
 DEFINE_bool(incremental_marking, true, "use incremental marking")
 DEFINE_bool(incremental_marking_steps, true, "do incremental marking steps")
 DEFINE_bool(trace_incremental_marking, false,
             "trace progress of the incremental marking")
 DEFINE_bool(track_gc_object_stats, false,
             "track object counts and memory usage")
 #ifdef VERIFY_HEAP
 DEFINE_bool(verify_heap, false, "verify heap pointers before and after GC")
@@ skipping 305 matching lines @@
 #undef DEFINE_bool
 #undef DEFINE_int
 #undef DEFINE_string
 #undef DEFINE_implication
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS