GitLab

Attempting to create ShelfWidget while shelf is in-app is causing
a crash because ShelfWidget::DelegateView::UpdateOpaqueBackground is
called before the widget is initialized.

Moving that call from ShelfWidget::DelegateView constructor into
ShelfWidget::DelegateView::OnWidgetInitialized.

Added a unit test.

Bug: 1021662
Test: manual, DisplayManagerTest.ExitMirrorModeInTabletMode
Change-Id: I32a5f91c834d673b109ab518bc2600908d8dea5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1902273Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Commit-Queue: Vladislav Kaznacheev <kaznacheev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713464}