Revert of Revert "Revert of Reland: Switch WindowedNotificationObserver to use base::RunLoop....

Revert of Revert "Revert of Reland: Switch WindowedNotificationObserver to use base::RunLoop. (patchset #3 id… (patchset #11 id:200001 of https://codereview.chromium.org/2740783003/ )

Reason for revert:
Probable cause for failing browser test NavigatingExtensionPopupBrowserTest.DownloadViaPost in https://uberchromegw.corp.google.com/i/chromium.mac/builders/Mac10.11%20Tests/builds/11339

Original issue's description:
> Reland #2: Switch WindowedNotificationObserver to use base::RunLoop.
> 
> Now it will quit the message loop immediately after receiving the
> notification. Also it does not allow nested tasks anymore.
> 
> Previous CL (https://codereview.chromium.org/2720513003) is in patchset #1.
> Added fixes for:
>  - browser_tests.NavigatingExtensionPopupBrowserTest.DownloadViaPost with PlzNavigate;
>  - interactive_ui_tests.ConstrainedWindowViewTest.NavigationOnBackspace.
> Also rephrased comment in print_preview_dialog_controller_browsertest.cc.
> 
> BUG=668707
> 
> Review-Url: https://codereview.chromium.org/2740783003
> Cr-Commit-Position: refs/heads/master@{#466016}
> Committed: https://chromium.googlesource.com/chromium/src/+/25911df55b8f939560df1f664f8cc8941ddc4677

TBR=jam@chromium.org,vabr@chromium.org,ahest@yandex-team.ru
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=668707

[tdanderson, 2017-04-20 19:08:57]

The CQ bit was checked by tdanderson@chromium.org

[tdanderson, 2017-04-20 19:08:58]

Created Revert of Revert "Revert of Reland: Switch WindowedNotificationObserver
to use base::RunLoop. (patchset #3 id…

[commit-bot: I haz the power, 2017-04-20 19:10:21]

The CQ bit was unchecked by commit-bot@chromium.org

[tdanderson, 2017-04-20 19:12:20]

The CQ bit was checked by tdanderson@chromium.org

[commit-bot: I haz the power, 2017-04-20 19:13:36]

The CQ bit was unchecked by commit-bot@chromium.org

[tdanderson, 2017-04-20 19:20:03]

The CQ bit was checked by tdanderson@chromium.org

[commit-bot: I haz the power, 2017-04-20 19:22:11]

The CQ bit was unchecked by commit-bot@chromium.org

[xlai (Olivia), 2017-04-20 19:38:21]

The CQ bit was checked by xlai@chromium.org

[commit-bot: I haz the power, 2017-04-20 19:39:43]

The CQ bit was unchecked by commit-bot@chromium.org

[tdanderson, 2017-04-20 20:36:45]

The CQ bit was checked by tdanderson@chromium.org

[commit-bot: I haz the power, 2017-04-20 20:38:19]

The CQ bit was unchecked by commit-bot@chromium.org

[tdanderson, 2017-04-20 20:54:36]

On 2017/04/20 19:08:58, tdanderson wrote:
> Created Revert of Revert "Revert of Reland: Switch
WindowedNotificationObserver
> to use base::RunLoop. (patchset #3 id…

The bots seem to have cycled green without this revert landing,
so I am going to close it out.