Fix uninitialized data error in HistoryURLProvider.
Fix uninitialized data error in HistoryURLProvider.

Reported by valgrind. See bug for more dteails.

BUG=528067

Review URL: https://codereview.chromium.org/1310213010

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#347303}

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