Revert of Move content's shell connections to the IO thread

services/shell/public/cpp/lib/connector_impl.h

Index: services/shell/public/cpp/lib/connector_impl.h
diff --git a/services/shell/public/cpp/lib/connector_impl.h b/services/shell/public/cpp/lib/connector_impl.h
index 003e3fdd990429704b4348b124aab197712a2203..9ab5bebefd427f8f34ea05de320147011baac915 100644
--- a/services/shell/public/cpp/lib/connector_impl.h
+++ b/services/shell/public/cpp/lib/connector_impl.h
@@ -28,12 +28,10 @@
   std::unique_ptr<Connection> Connect(ConnectParams* params) override;
   std::unique_ptr<Connector> Clone() override;
 
-  bool BindIfNecessary();
-
   mojom::ConnectorPtrInfo unbound_state_;
   mojom::ConnectorPtr connector_;
 
-  base::ThreadChecker thread_checker_;
+  std::unique_ptr<base::ThreadChecker> thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(ConnectorImpl);
 };