Rolling v8/build to 679c9fd3fa7390897bcf6891f0dc57a5e5dced0d

Rolling v8/tools/mb to d939c7d364f0565ac2ddcae09aafe01c9bf8007d

TBR=machenbach@chromium.org,vogelheim@chromium.org,hablich@chromium.org

Review-Url: https://codereview.chromium.org/2293333002
Cr-Commit-Position: refs/heads/master@{#39035}