Fix chromium-style warning after https://codereview.chromium.org/1639623003/
Fix chromium-style warning after https://codereview.chromium.org/1639623003/

Also fix a -Wsign-compare warning.

BUG=426656,82385
TBR=robliao@chromium.org

Review URL: https://codereview.chromium.org/1679743004 .

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#374370}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk