WebUI styleguide: Allow usage of ES6 template strings (backticks).

Bug: 671426
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I4efa74ee25f3c5e6a09035576ec1d66831b7ee6e
Reviewed-on: https://chromium-review.googlesource.com/696265
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#511362}
6 files changed