Expose counters in javascript.

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 285 matching lines @@
             '../../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/gc-extension.cc',
             '../../src/extensions/gc-extension.h',
+            '../../src/extensions/counters-extension.cc',
+            '../../src/extensions/counters-extension.h',
             '../../src/factory.cc',
             '../../src/factory.h',
             '../../src/fast-dtoa.cc',
             '../../src/fast-dtoa.h',
             '../../src/fixed-dtoa.cc',
             '../../src/fixed-dtoa.h',
             '../../src/flag-definitions.h',
             '../../src/flags.cc',
             '../../src/flags.h',
             '../../src/frames-inl.h',
@@ skipping 675 matching lines @@
             }],
           ],
           'dependencies': [
             'v8'
           ],
         },
       ],
     }],
   ],
 }