Run the DOMStorageBrowserTest.SanityCheck against the mojo based implementation.

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 4f7ea18a20f7828d30c4d0c4581fc30638bfbb9a..96e2cee81d7cfa739884aba795f18909a534aef5 100644
--- a/content/browser/dom_storage/dom_storage_context_wrapper.cc
+++ b/content/browser/dom_storage/dom_storage_context_wrapper.cc
@@ -98,6 +98,15 @@ class DOMStorageContextWrapper::MojoState {
     level_db_wrappers_.erase(origin);
   }
 
+  void OnUserServiceConnectionComplete() {
+    CHECK_EQ(shell::mojom::ConnectResult::SUCCEEDED,
+             user_service_connection_->GetResult());
+  }
+
+  void OnUserServiceConnectionError() {
+    CHECK(false);
+  }
+
   // Part of our asynchronous directory opening called from OpenLocalStorage().
   void OnDirectoryOpened(filesystem::FileError err);
   void OnDatabaseOpened(leveldb::DatabaseError status);
@@ -143,6 +152,12 @@ void DOMStorageContextWrapper::MojoState::OpenLocalStorage(
     user_service_connection_ =
         connector_->Connect(user_service::kUserServiceName);
     connection_state_ = CONNECTION_IN_PROGRESS;
+    user_service_connection_->AddConnectionCompletedClosure(
+        base::Bind(&MojoState::OnUserServiceConnectionComplete,
+                   weak_ptr_factory_.GetWeakPtr()));
+    user_service_connection_->SetConnectionLostClosure(
+        base::Bind(&MojoState::OnUserServiceConnectionError,
+                   weak_ptr_factory_.GetWeakPtr()));
 
     if (!subdirectory_.empty()) {
       // We were given a subdirectory to write to. Get it and use a disk backed