Update V8 to version 3.20.15.5

DEPS

 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 
 vars = {
   # Use this googlecode_url variable only if there is an internal mirror for it.
   # If you do not know, use the full path while defining your new deps entry.
   "googlecode_url": "http://%s.googlecode.com/svn",
   "sourceforge_url": "http://svn.code.sf.net/p/%(repo)s/code",
   "webkit_trunk": "http://src.chromium.org/blink/trunk",
   "nacl_trunk": "http://src.chromium.org/native_client/trunk",
@@ skipping 16 matching lines @@
   # checkouts and the other for Git checkouts.
   "ffmpeg_revision": "214392",
   "ffmpeg_hash": "894e6f715645528e815aee2dad45b59704238dcd",
 
   "sfntly_revision": "134",
   "skia_revision": "10680",
   "skia_hash": "8f4825bfb1da69439e1e96a0c6ea04488757d95e",
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.
-  "v8_revision": "16142",
+  "v8_revision": "16159",
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.
   "webrtc_revision": "4520",
   "jsoncpp_revision": "248",
   "nss_revision": "209026",
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling swarm_client
   # and whatever else without interference from each other.
   "swarm_revision": "213621",
@@ skipping 566 matching lines @@
     "pattern": ".",
     "action": ["python", "src/build/gyp_chromium"],
   },
   {
     # Check for landmines (reasons to clobber the build).
     "name": "landmines",
     "pattern": ".",
     "action": ["python", "src/build/landmines.py"],
   },
 ]