Update V8 to version 4.2.38 (based on b004b1d821e28ffec8212a7cdf46b84cbdf74b67).

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/888863003

Cr-Commit-Position: refs/heads/master@{#313917}

DEPS

@@ -47,7 +47,7 @@ vars = {
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.
   'v8_branch': 'trunk',
-  'v8_revision': '95c02f1a59fece9f29a6c9511cb0bf016e9ab815',
+  'v8_revision': '724fef00c885c45f86216bbd21b69db689a2141b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.