Perform scavenge in idle tasks.

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 716 matching lines @@
         '../../src/heap/incremental-marking.cc',
         '../../src/heap/incremental-marking.h',
         '../../src/heap/mark-compact-inl.h',
         '../../src/heap/mark-compact.cc',
         '../../src/heap/mark-compact.h',
         '../../src/heap/object-stats.cc',
         '../../src/heap/object-stats.h',
         '../../src/heap/objects-visiting-inl.h',
         '../../src/heap/objects-visiting.cc',
         '../../src/heap/objects-visiting.h',
+        '../../src/heap/scavenge-job.h',
+        '../../src/heap/scavenge-job.cc',
         '../../src/heap/scavenger-inl.h',
         '../../src/heap/scavenger.cc',
         '../../src/heap/scavenger.h',
         '../../src/heap/slots-buffer.cc',
         '../../src/heap/slots-buffer.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',
@@ skipping 1336 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }