Makes it so a node can only the root of one connection at a time

mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc

Index: mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc
diff --git a/mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc b/mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc
index a949da8579657db686c3ebd51cdf0bf7b3973f45..4a69ff099884366632244f94937028abac2a5b31 100644
--- a/mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc
+++ b/mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc
@@ -478,6 +478,7 @@ class EmbedTransaction : public ViewManagerTransaction {
  private:
   // Overridden from ViewManagerTransaction:
   virtual void DoCommit() OVERRIDE {
+    GetAndAdvanceNextServerChangeId();
     service()->Embed(url_, node_id_, ActionCompletedCallback());
   }
   virtual void DoActionCompleted(bool success) OVERRIDE {