Attaching expected video for reference

Deleted: Expected_TabFocus.mp4 17.9 MB

Expected_TabFocus.mp4 17.9 MB Download

I have investigated and got some more insights:
- This is not a regression.
   - also reproduced at 67.0.3396.99 on stable-channel samus.
- This has been happening on popup notification.
   - The repro step describes that it is on a popup notification, not message center.
   - Screenshot in the Expected_TabFocus.PNG seems to be that of message center.
- This is not related to expand/collapse.
- This is not limited to the screenshot notification.
- As a separate issue, still, there's a similar issue with Unified Message Center (the one which appear above ubertray) as well. (I bet that this why it turned visible from M70)


FYI, here's the reason why the original report contains expand/collapse in repro step.
- This needs to be allow tab focusing by focusing the window.
- In order to do that we need to click somewhere on a popup notification that doesn't close itself.
- The expand-collapse button is one that satisfies 2.
- Another example is a gray area right to "COPY TO CLIPBOARD" button.
So IIUC we can just left-click on the gray area next to the action button, at step 2.

I'll fix the issue on Unified System Tary first because it's a true regression.

A blue rectangle is drawn on MessageView by MessageView::OnPaint but it's hidden behind several views now.
- MessageView::background_view_ which draws the white solid background of each notification
- LargeImageView when notification contains an image
Additionally, in the Unified notification center, the rounded corner of the parent view cuts off the rectangle.

Deleted: notification_without_background.png 23.0 KB

	notification_without_background.png 23.0 KB View Download

https://crrev.com/c/1195297

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/14cb873774626f8b34aa28777f3ed913d6d91a32

commit 14cb873774626f8b34aa28777f3ed913d6d91a32
Author: Tetsui Ohkubo <tetsui@chromium.org>
Date: Fri Aug 31 14:41:27 2018

Remove background_view from MessageView.

MessageView had |background_view_| in order to just change paint
ordering of Background and Border. It caused focus painter not to be
painted in the right order. We no longer have shadow borders so we
don't have to change the paint ordering.

TEST=manual
BUG= 877939 

Change-Id: I226701e680b38920edc5ff34fa1cb6b19ef93ad3
Reviewed-on: https://chromium-review.googlesource.com/1195297
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588021}
[modify] https://crrev.com/14cb873774626f8b34aa28777f3ed913d6d91a32/ash/system/message_center/arc/arc_notification_view.cc
[modify] https://crrev.com/14cb873774626f8b34aa28777f3ed913d6d91a32/ui/message_center/views/message_view.cc
[modify] https://crrev.com/14cb873774626f8b34aa28777f3ed913d6d91a32/ui/message_center/views/message_view.h