Rolling v8/tools/clang to 91e7a78800b5849e27e098daa42e6ae8650ad322

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

Review URL: https://codereview.chromium.org/1316403006

Cr-Commit-Position: refs/heads/master@{#30551}