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

Automatically generated ARCMigrate commit
Notable issues:
 * This temporarily splits ui_internal into two targets to simplify review. The targets
are merged in a dependent CL.

BUG=624363
TEST=None

Review-Url: https://codereview.chromium.org/2804703002
Cr-Commit-Position: refs/heads/master@{#463232}
14 files changed