Provide "freeBuffer()" primitive for testing under ASan.

tools/gyp/v8.gyp

 # 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 314 matching lines @@
         '../../src/dtoa.h',
         '../../src/effects.h',
         '../../src/elements-kind.cc',
         '../../src/elements-kind.h',
         '../../src/elements.cc',
         '../../src/elements.h',
         '../../src/execution.cc',
         '../../src/execution.h',
         '../../src/extensions/externalize-string-extension.cc',
         '../../src/extensions/externalize-string-extension.h',
+        '../../src/extensions/free-buffer-extension.cc',
+        '../../src/extensions/free-buffer-extension.h',
         '../../src/extensions/gc-extension.cc',
         '../../src/extensions/gc-extension.h',
         '../../src/extensions/statistics-extension.cc',
         '../../src/extensions/statistics-extension.h',
         '../../src/factory.cc',
         '../../src/factory.h',
         '../../src/fast-dtoa.cc',
         '../../src/fast-dtoa.h',
         '../../src/fixed-dtoa.cc',
         '../../src/fixed-dtoa.h',
@@ skipping 752 matching lines @@
         }],
         ['v8_compress_startup_data=="bz2"', {
           'libraries': [
             '-lbz2',
           ]
         }],
       ],
     },
   ],
 }