GitLab

This cl creates the event change class that will be used to send primary
account change notifications to the observers. This cl also adds unit
tests for PrimaryAccountChangeEvent.

Design Doc: go/consent-aware-api-dd

Bug: 1046746
Change-Id: I7c82dd3ba8c3296ec457fbe94893550f27386a58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2592999Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Tanmoy Mollik <triploblastic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838025}