[ObjC ARC] Converts ios/chrome/browser/ui/util:util to ARC.

Automatically generated ARCMigrate commit
Notable issues:static_cast changed to __bridge cast.
BUG=624363
TEST=None

Review-Url: https://codereview.chromium.org/2819283004
Cr-Commit-Position: refs/heads/master@{#467946}
16 files changed