Revert "Restore web app windows when session restore is enabled."

This partially reverts commit 9aa56a4612d13c491e60c9500915dbda2ac9f2a1.

Although this fixes issue 938759, it introduces issue 953965 which is not easily fixed.
I'll add more detail on the right fix in issue 938759.

The piece that ensures the default browser prompt isn't shown in an app window
is kept as this is still useful.

Original change's description:
> Restore web app windows when session restore is enabled.
>
> App windows are currently only restored through session restore when
> Chrome is restarted on Chrome OS.
>
> This CL includes standalone web app windows on other desktop platforms
> in session restore. This ensures that when Chrome is quit with web apps
> open, those web apps will be reopened if the user has opted into
> "continue where I left off" upon restarting. Session service tests are
> updated to account for this change in behaviour.
>
> The default browser prompt is also updated to ensure it never shows in
> an app window (which may now be the "last active" browser object at
> startup depending on the order in which the windows are restored).
>
> BUG=938759
>
> Change-Id: I4f0927e03b3c472f67e8dbee81233d6b453a7d68
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1504477
> Commit-Queue: Dominick Ng <dominickn@chromium.org>
> Reviewed-by: Tommy Martino <tmartino@chromium.org>
> Reviewed-by: Chris Hamilton <chrisha@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#639187}

TBR=chrisha@chromium.org,tmartino@chromium.org,dominickn@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 938759
Change-Id: I72534ece9254656c92bfb634bc1a464311e4146f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1657508
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Commit-Queue: Raymes Khoury <raymes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669551}
3 files changed