chrome/browser/autofill: scoped_ptr -> unique_ptr

In response to
https://groups.google.com/a/chromium.org/d/msg/chromium-dev/roY78iTblYc/6juu-QucCgAJ,
which I hope was not an April Fool's joke. :)

BUG=600221

Review URL: https://codereview.chromium.org/1857663002

Cr-Commit-Position: refs/heads/master@{#384900}
10 files changed