GitLab

Use of TransientWindowClient and ActivationClient allow the same
implementation to work in both classic and Mash.

Bug: 640365
Change-Id: I10324dce04bb014c09d04f45c0be6e691017a648
Reviewed-on: https://chromium-review.googlesource.com/c/1271403Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600119}