Try to flush DOMStorage too when ending the browsing session.

content/browser/dom_storage/dom_storage_context_wrapper.cc

Index: content/browser/dom_storage/dom_storage_context_wrapper.cc
diff --git a/content/browser/dom_storage/dom_storage_context_wrapper.cc b/content/browser/dom_storage/dom_storage_context_wrapper.cc
index be4ffb4c0b619f129745bb2b14a1d742ccb5f950..5b4ca965e260eaf315e209b97ad4219b18499d21 100644
--- a/content/browser/dom_storage/dom_storage_context_wrapper.cc
+++ b/content/browser/dom_storage/dom_storage_context_wrapper.cc
@@ -257,6 +257,12 @@ void DOMStorageContextWrapper::Flush() {
     mojo_state_->Flush();
 }
 
+scoped_refptr<base::SequencedTaskRunner>
+DOMStorageContextWrapper::GetSequencedTaskRunner(
+    DOMStorageTaskRunner::SequenceID id) {
+  return context_->task_runner()->GetSequencedTaskRunner(id);
+}
+
 void DOMStorageContextWrapper::OpenLocalStorage(
     const url::Origin& origin,
     mojom::LevelDBWrapperRequest request) {