Update V8 to version 4.2.56 (based on 996fa7d36e4b033794a306f89aae58557e70bc8b).

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/904063003

Cr-Commit-Position: refs/heads/master@{#315112}

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': '0aa5f75929fa3b383ec749555e045e47199ba6d5',
+  'v8_revision': '08cdd67a32b943b17702ab7dafa56456072fafce',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.