Prevent tabs sync during browser shutdown.

Prevent tabs sync during browser shutdown.

Browser shutdown invokes closing of open tabs and firing
of OnLocalTabModified event. Thus other clients recieve notifications
that all tabs are closed. Current CL fixes this issue.

BUG=702604
R=zea@chromium.org, skym@chromium.org

[skym, 2017-03-16 20:18:07]

skym@chromium.org changed reviewers:
+ pnoland@chromium.org

[skym, 2017-03-16 20:18:08]

Hey, I really hate to do this to you, but we're also actively trying to switch
from the NotificationsService/API to WebContentsObserver for sessions changes.
See https://codereview.chromium.org/2753753005/ . I'm not terribly familiar with
either event system, hopefully the same results can be achieved through
WebContentsObserver, +pnoland.

Also, can you create a bug for such a non-trivial change? I'm not sure I fully
follow why this would be the correct behavior. If you're "On startup" setting is
to "Continue where you left off", then I'd agree this behavior seems clearly
correct. But if your "On startup" setting is something else, it seems a bit
ambiguous. Would be good to have somewhere to discuss this.

[Alexey Seren, 2017-03-17 13:57:13]

Description was changed from

==========
Prevent tabs sync during browser shutdown.

Browser shutdown invokes closing of open tabs and firing
of OnLocalTabModified event. Thus other clients recieve notifications
that all tabs are closed. Current CL fixes this issue.

BUG=

R=zea@chromium.org, skym@chromium.org
==========

to

==========
Prevent tabs sync during browser shutdown.

Browser shutdown invokes closing of open tabs and firing
of OnLocalTabModified event. Thus other clients recieve notifications
that all tabs are closed. Current CL fixes this issue.

BUG=702604

R=zea@chromium.org, skym@chromium.org
==========

[Alexey Seren, 2017-03-17 14:03:51]

Hello skym!

Thank you for reviewing this CL. 
I can update it basing on WebContentsObserver when
https://codereview.chromium.org/2753753005/ will be merged.

The corresponding bug has been created:
https://bugs.chromium.org/p/chromium/issues/detail?id=702604

[Alexey Seren, 2017-03-17 17:42:52]

Hey Skim,

You are right about "On startup" setting behaviour. 
NotificationService have to check it before assuming that tabs close shouldn't
be synced. I will fix this in the next patchset.

Thank you.

[Patrick Noland, 2017-03-23 22:43:33]

Now that https://codereview.chromium.org/2753753005/ has landed, you should be
able to rebase this. I'd prefer that you avoid using the Notification Service at
all. Instead I think you can accomplish what you want by checking the browser
count and browser_shutdown::ShutdownType in
BrowserListRouterHelper::OnBrowserRemoved.