GitLab

This CL changes some classes in ui/views/accessibility/ and view_tracker.{h,cc} to use ScopedObserver.

Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=940796
Change-Id: Iee16691098fae2e3cba4f11a9d970181ca28f659
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1558558
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714983}