Restore KeyedServiceFactory diagnostics for context use-after-destroy.

components/keyed_service/core/refcounted_keyed_service_factory.cc

Index: components/keyed_service/core/refcounted_keyed_service_factory.cc
diff --git a/components/keyed_service/core/refcounted_keyed_service_factory.cc b/components/keyed_service/core/refcounted_keyed_service_factory.cc
index 7c44c2ce3893fcf79297864fe0041e5914712900..7afecda34f6676c1c5aa3d3dac84ad66effad3b7 100644
--- a/components/keyed_service/core/refcounted_keyed_service_factory.cc
+++ b/components/keyed_service/core/refcounted_keyed_service_factory.cc
@@ -28,6 +28,12 @@ void RefcountedKeyedServiceFactory::SetTestingFactory(
   // destruction.
   bool add_context = ArePreferencesSetOn(context);
 
+  // Ensure that |context| is not marked as stale (e.g., due to it aliasing an
+  // instance that was destroyed in an earlier test) in order to avoid accesses
+  // to |context| in |ContextShutdown| from causing
+  // |AssertBrowserContextWasntDestroyed| to raise an error.
+  MarkContextLive(context);
+
   // We have to go through the shutdown and destroy mechanisms because there
   // are unit tests that create a service on a context and then change the
   // testing service mid-test.