Convert most of /chrome/browser to use ARC

See https://chromium.googlesource.com/chromium/src/+/main/docs/mac/arc.md
for information about this conversion.

This (plus more files) was previously committed as
https://crrev.com/c/4546398 but reverted. This CL omits the ARCifying
of complicated files, but ARCifies the files in /chrome/browser with
straightforward, non-controversial changes.

Bug: 1280317
Change-Id: Ibb34c35f8baa7616f13638e1f7a1d2c67b419a6e
Include-Ci-Only-Tests: true
Cq-Include-Trybots: luci.chromium.try:ios-blink-dbg-fyi
Cq-Include-Trybots: luci.chrome.try:mac-chrome
Validate-Test-Flakiness: skip
Low-Coverage-Reason: Doing core refactoring across all of Chromium; I do not own this code
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4566446


Auto-Submit: Avi Drissman <avi@chromium.org>
Reviewed-by: Leonard Grey <lgrey@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1149425}