Fixing clang-tidy warning.

Bug: v8:8015
Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I641c72959470471747221f94da545a053dfcc0b0
Reviewed-on: https://chromium-review.googlesource.com/1228064Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Florian Sattler <sattlerf@google.com>
Cr-Commit-Position: refs/heads/master@{#55977}