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

Automatically generated ARCMigrate commit
Notable issues:
 * This converts BVC to ARC, so please review with extra scrutiny.

BUG=624363
TEST=None

Review-Url: https://codereview.chromium.org/2798903003
Cr-Commit-Position: refs/heads/master@{#463244}
6 files changed