Add CallOnce() and simple LazyInstance implementation.

src/SConscript

 # Copyright 2011 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 82 matching lines @@
     lithium.cc
     liveedit.cc
     liveobjectlist.cc
     log-utils.cc
     log.cc
     mark-compact.cc
     messages.cc
     objects.cc
     objects-printer.cc
     objects-visiting.cc
+    once.cc
     parser.cc
     preparser.cc
     preparse-data.cc
     profile-generator.cc
     property.cc
     regexp-macro-assembler-irregexp.cc
     regexp-macro-assembler.cc
     regexp-stack.cc
     rewriter.cc
     runtime.cc
@@ skipping 286 matching lines @@
       snapshot_cc = 'snapshot.cc'
     snapshot_obj = context.ConfigureObject(env, snapshot_cc, CPPPATH=['.'])
   else:
     snapshot_obj = empty_snapshot_obj
   library_objs = [non_snapshot_files, libraries_obj, experimental_libraries_obj, snapshot_obj]
   return (library_objs, d8_objs, [mksnapshot], preparser_objs)
 
 
 (library_objs, d8_objs, mksnapshot, preparser_objs) = ConfigureObjectFiles()
 Return('library_objs d8_objs mksnapshot preparser_objs')