The previous roll seems to break C++17 mode of windows build.
The culprit was r335084, and that was reverted at r335516.
https://bugs.llvm.org/show_bug.cgi?id=37935

That should work fine again after the next roll.

Sorry, goma is blocking current roll and we are fixing the issue.
https://chromium-review.googlesource.com/c/chromium/src/+/1114922

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cbf76818d0f7e88d489f18ada04a4077e594daec

commit cbf76818d0f7e88d489f18ada04a4077e594daec
Author: Nico Weber <thakis@chromium.org>
Date: Wed Jun 27 11:46:07 2018

Roll clang 335091:335608.

Ran `tools/clang/scripts/upload_revision.py 335608`.

Bug:  855772 
Change-Id: Idb1947be31a99371cbddaa7f214d64858ef15d9c
Reviewed-on: https://chromium-review.googlesource.com/1114922
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570732}
[modify] https://crrev.com/cbf76818d0f7e88d489f18ada04a4077e594daec/tools/clang/scripts/update.py

Looks like this might stick.

The next roll is happening at  issue 857012 .