Fix a QuicStreamSequencerBuffer logging issue caused by inapproriate itoa function.
Fix a QuicStreamSequencerBuffer logging issue caused by inapproriate itoa function.

R=rch@chromium.org
BUG=607951

Review-Url: https://codereview.chromium.org/1954183002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#392130}

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