Converts  ios/chrome/browser/ui/bookmarks:bookmarks_arc to ARC.

Automatically generated ARCMigrate commit
Notable issues:
* automatic rewriter script rewrote "return scoped_foo.autorelease();" to "return scoped_foo = nil;" causing EG test failures

BUG=624363
TEST=None

Initially was failing EG tests, see Notable issues for steps taken.

Review-Url: https://codereview.chromium.org/2741413005
Cr-Commit-Position: refs/heads/master@{#456684}
18 files changed