Switch WindowedNotificationObserver to use base::RunLoop.

extensions/test/extension_test_notification_observer.cc

Index: extensions/test/extension_test_notification_observer.cc
diff --git a/extensions/test/extension_test_notification_observer.cc b/extensions/test/extension_test_notification_observer.cc
index 0e4d75d0ccdcbfa8cfe6e07dfb27c4b3ab52ef06..a18e75fc4914fef6ae2838f5de18fed360b3aa9e 100644
--- a/extensions/test/extension_test_notification_observer.cc
+++ b/extensions/test/extension_test_notification_observer.cc
@@ -140,6 +140,8 @@ void ExtensionTestNotificationObserver::Watch(
 
 void ExtensionTestNotificationObserver::Wait() {
   observer_->Wait();
+  // TODO(...): Find out why tests fail without it.

[Alexander Semashko, 2017/02/21 21:33:47]

Please advise what to do here, e.g. assign this TODO to somebody or create a
bug.
As to what is going on here: some tests started failing after the removal of
implicit deferred quit in the WindowedNotificationObserver. This means that
waiting for the notification itself is not sufficient. What is needed here is to
find out what is missing, and (probably) add code to wait for that event(s). Or
just leave RunAllPending if it turns out that these events do not involve other
threads/processes and happen without any delay.

[Devlin, 2017/02/22 00:26:48]

Filing a bug would probably be best here, ideally with a list of the tests that
are affected.

[Alexander Semashko, 2017/02/22 17:10:08]

Done, https://bugs.chromium.org/p/chromium/issues/detail?id=695073

+  content::RunAllPendingInMessageLoop();
 
   registrar_.RemoveAll();
   observer_.reset();