Update V8 DEPS.
Update V8 DEPS.

Rolling v8/tools/clang to 6f9d79914087cffd820021c3bb1155ad44f4b435

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/904793003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#26474}

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