Minor fix for Media.Audio.XXXXInputBufferFrameSizeMac UMA stats
Minor fix for Media.Audio.XXXXInputBufferFrameSizeMac UMA stats

BUG=549021

Review URL: https://codereview.chromium.org/1699823002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#375442}

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