Add FLAG_trace_maps

build/toolchain.gypi

 # 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 834 matching lines @@
         ],
       },  # DebugBase2
       # Common settings for the Debug configuration.
       'DebugBaseCommon': {
         'abstract': 1,
         'defines': [
           'ENABLE_DISASSEMBLER',
           'V8_ENABLE_CHECKS',
           'OBJECT_PRINT',
           'VERIFY_HEAP',
-          'DEBUG'
+          'DEBUG',
+          'TRACE_MAPS'
         ],
         'conditions': [
           ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd" or \
             OS=="qnx"', {
             'cflags': [ '-Woverloaded-virtual', '<(wno_array_bounds)', ],
           }],
           ['OS=="linux" and v8_enable_backtrace==1', {
             # Support for backtrace_symbols.
             'ldflags': [ '-rdynamic' ],
           }],
@@ skipping 106 matching lines @@
                 'OptimizeReferences': '2',
                 'EnableCOMDATFolding': '2',
               },
             },
           }],  # OS=="win"
         ],  # conditions
       },  # Release
     },  # configurations
   },  # target_defaults
 }