amyroberts@, I assumed that it wasn't in the deck on purpose (ie. we did not want that and the icon on the tab would play that role), is this correct?

mlamourni@ yes, that was the intention. I don't feel strongly about the dialog, but I'd note that we don't currently pop one when closing a page playing audio or when in a hangout. 

I believe it is especially useful as the PiP video doesn't have any Chrome UI. User may think it is not related to Chrome and simply want to continue playing video while closing browser that is already in a minimized state.

Fair point. +srahim for guidance on what the dialog should say. 

Quick suggestion for something less verbose than the Safari dialog:

Quit Chrome?
The picture-in-picture video will stop playing.
Cancel | Quit

fbeaufort@ does Safari show a different message when closing a window (ie. multiple tabs)? or just closing the tab playing in PIP?

In other words, I'm wondering when we should show the message? Only when closing Chrome or when closing the tab regardless of the context?

Messages are indeed different when closing a single tab and a window. See screenshots attached.

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srahim@ that sounds good to me when closing a window. 

Should it be worded any differently when closing a tab? 

Hm, I'd say the message could be the same regardless of quitting a tab or a window - the main point is you're about to quit Chrome and the PIP will stop playing.
Unless I'm missing something, I think it's OK to use the same message for both tab or window.

Proposal SGTM. Assigning to Jennifer to implement.

Should we also show the warning when navigating away from the page we triggered PiP?  See screenshot for slightly different messaging.

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The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e45a7339b7867f398e271775bc2c495fee3b5b3b

commit e45a7339b7867f398e271775bc2c495fee3b5b3b
Author: Jennifer Apacible <apacible@chromium.org>
Date: Fri Jun 22 20:42:35 2018

[Picture in Picture] Add strings for confirmation dialog.

These strings will be used for the dialog that appears when the user:
- is closing the tab or window that initiated a Picture-in-Picture
session, or
- is navigating away from a page that initiated a Picture-in-Picture
session.

Dialog implementation is in progress.

Bug:  809982 
TBR: grt@chromium.org
Change-Id: I060fb2f21fc93361aeb11f4b605b5012d369e28c
Reviewed-on: https://chromium-review.googlesource.com/1112304
Commit-Queue: apacible <apacible@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569750}
[modify] https://crrev.com/e45a7339b7867f398e271775bc2c495fee3b5b3b/chrome/app/generated_resources.grd

The team is moving towards deprecating warning dialogs. In a similar vein as not showing any warnings when the Casting tab is closed, we will not show warnings for now.

Open to revisiting if we get overwhelming feedback from users that this is a problem.