Update V8 DEPS.
Update V8 DEPS.

Rolling v8/tools/clang to b66ad18bb147f02b74b207358140371382b0ef35

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/1281053003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#30100}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh