Update V8 to version 3.31.40 (based on 8138bb5b85060b06b3f9d10affec32…

…4fee0d8d7a).

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/741503005

Cr-Commit-Position: refs/heads/master@{#306789}

DEPS

@@ -49,7 +49,7 @@ vars = {
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.
   'v8_branch': 'trunk',
-  'v8_revision': 'dfec52e2f3e073cfe28d0041f6d7c657d9b9486f',
+  'v8_revision': '5e7bfaf5530837b94fa0c05189c0ab601e3a6355',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.