Restore thread check in KeyedService factories.

components/keyed_service/core/keyed_service_base_factory.cc

Index: components/keyed_service/core/keyed_service_base_factory.cc
diff --git a/components/keyed_service/core/keyed_service_base_factory.cc b/components/keyed_service/core/keyed_service_base_factory.cc
index 48643305759bcc97660622b7d38adfefcfbbbdfa..07be770167a1a04cb526a63d1581b93ea1458fb7 100644
--- a/components/keyed_service/core/keyed_service_base_factory.cc
+++ b/components/keyed_service/core/keyed_service_base_factory.cc
@@ -81,9 +81,7 @@ KeyedServiceBaseFactory::GetAssociatedPrefRegistry(
 
 void KeyedServiceBaseFactory::AssertContextWasntDestroyed(
     base::SupportsUserData* context) const {
-  // TODO(crbug.com/701326): We should DCHECK(CalledOnValidThread()) here, but
-  // currently some code doesn't do service getting on the main thread.
-  // This needs to be fixed and DCHECK should be restored here.
+  DCHECK(CalledOnValidThread());
   dependency_manager_->AssertContextWasntDestroyed(context);
 }