Fix Visual Studio warning on single file compilation BUG=615402 Review-Url: https://codereview.chromium.org/2018733003 Cr-Original-Commit-Position: refs/heads/master@{#396693} Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src Cr-Mirrored-Commit: a7e95b0468908825cdafa072ed1b8f99f3859a93