Remove NOTIFICATION_GLOBAL_ERRORS_CHANGED

Replace it with an observer interface on GlobalErrorService.

Change-Id: Ief1d6c231684e886a17931be7355ca6a6cabda72
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1670054
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672141}
18 files changed