GitLab

Introduce a common views::test::WidgetVisibleWaiter helper class to
enable tests to easily wait for a given widget to become visible, and
use it in place of places that had similar functionality.

Bug: None
Change-Id: I4fda7baeef12ae33f47a47393a58396f917b65e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2151343Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#759725}