Update V8 to version 4.7.51.

DEPS

 # This file is used to manage the dependencies of the Chromium src repo. It is
 # used by gclient to determine what version of each dependency to check out, and
 # where.
 #
 # For more information, please refer to the official documentation:
 #   https://sites.google.com/a/chromium.org/dev/developers/how-tos/get-the-code
 #
 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 #
@@ skipping 21 matching lines @@
   # If you do not know, use the full path while defining your new deps entry.
   'googlecode_url': 'http://%s.googlecode.com/svn',
   'webkit_revision': '5f48d9991f95a37584a4002c4e1165329ab5e183', # from svn revision 202229
   'chromium_git': 'https://chromium.googlesource.com',
   'libvpx_revision': 'ac1772e3db5c885b554f6a72ca9dbac4245cb0e2',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
   'skia_revision': '995b4bddd9a1eef933b0acb3ff03c98e7864a8f9',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.
-  'v8_revision': 'f8eb3135f2d004eee01931ed2f8af769c223afbd',
+  'v8_revision': 'd22619367ed37be9741b44502c26ea64ba620e9d',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling swarming_client
   # and whatever else without interference from each other.
   'swarming_revision': '49f046853671bbd5ab65509a8049d36ac0224714',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling ANGLE
   # and whatever else without interference from each other.
   'angle_revision': '4a693565dcfaba92f053db5c95e9338eac949245',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling build tools
@@ skipping 746 matching lines @@
     # migration completes (let's say Sep 1 2014).
     'name': 'check_git_config',
     'pattern': '.',
     'action': [
         'python',
         'src/tools/check_git_config.py',
         '--running-as-hook',
     ],
   },
 ]