Remove sweeper threads

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 570 matching lines @@
         '../../src/heap/mark-compact.h',
         '../../src/heap/objects-visiting-inl.h',
         '../../src/heap/objects-visiting.cc',
         '../../src/heap/objects-visiting.h',
         '../../src/heap/spaces-inl.h',
         '../../src/heap/spaces.cc',
         '../../src/heap/spaces.h',
         '../../src/heap/store-buffer-inl.h',
         '../../src/heap/store-buffer.cc',
         '../../src/heap/store-buffer.h',
-        '../../src/heap/sweeper-thread.h',
-        '../../src/heap/sweeper-thread.cc',
         '../../src/hydrogen-alias-analysis.h',
         '../../src/hydrogen-bce.cc',
         '../../src/hydrogen-bce.h',
         '../../src/hydrogen-bch.cc',
         '../../src/hydrogen-bch.h',
         '../../src/hydrogen-canonicalize.cc',
         '../../src/hydrogen-canonicalize.h',
         '../../src/hydrogen-check-elimination.cc',
         '../../src/hydrogen-check-elimination.h',
         '../../src/hydrogen-dce.cc',
@@ skipping 1085 matching lines @@
         }],
         ['v8_compress_startup_data=="bz2"', {
           'libraries': [
             '-lbz2',
           ]
         }],
       ],
     },
   ],
 }