Simplify implementation of Mutex.

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 401 matching lines @@
         '../../src/log-utils.h',
         '../../src/log.cc',
         '../../src/log.h',
         '../../src/macro-assembler.h',
         '../../src/mark-compact.cc',
         '../../src/mark-compact.h',
         '../../src/marking-thread.h',
         '../../src/marking-thread.cc',
         '../../src/messages.cc',
         '../../src/messages.h',
+        '../../src/mutex.cc',
+        '../../src/mutex.h',
         '../../src/natives.h',
         '../../src/objects-debug.cc',
         '../../src/objects-inl.h',
         '../../src/objects-printer.cc',
         '../../src/objects-visiting.cc',
         '../../src/objects-visiting.h',
         '../../src/objects.cc',
         '../../src/objects.h',
         '../../src/once.cc',
         '../../src/once.h',
@@ skipping 604 matching lines @@
         }],
         ['v8_compress_startup_data=="bz2"', {
           'libraries': [
             '-lbz2',
           ]
         }],
       ],
     },
   ],
 }