[mojo-edk] Fix potential buffer overflow in BrokerHost
[mojo-edk] Fix potential buffer overflow in BrokerHost

BUG=612613
R=ochang@chromium.org

Review-Url: https://codereview.chromium.org/1983363002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#394303}

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