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: I82a169545724fca7757b2fce6b64b56d1b6264ba
Reviewed-on: https://chromium-review.googlesource.com/1225794Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Florian Sattler <sattlerf@google.com>
Cr-Commit-Position: refs/heads/master@{#55980}