Update V8 to version 3.28.71.2 (merged r23115).

R=jkummerow@chromium.org
TBR=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/473843002

Cr-Commit-Position: refs/heads/master@{#289499}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289499 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -51,7 +51,7 @@ vars = {
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.
   "v8_branch": "trunk",
-  "v8_revision": "23085",
+  "v8_revision": "23117",
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.