Rolling v8/build/gyp to 0bb67471bca068996e15b56738fa4824dfa19de0

Rolling v8/buildtools to 15f5fc6fdb1795e2b99f66e5bc6c01e9fb62b436

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/1110063010

Cr-Commit-Position: refs/heads/master@{#28141}