Rolling v8/buildtools to 7274f1c726640bce4cd4c4198e1ee62a0b29bb89

Rolling v8/third_party/icu to 6d3b55dfa17d9a597c064eeef7ceac18c73184b7

Rolling v8/tools/clang to ec17c92cc70fcd8f5f39eaa17f3dbbd99e29c1f9

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

Review URL: https://codereview.chromium.org/1781313004

Cr-Commit-Position: refs/heads/master@{#34734}