Provide an API to the example window manager app that supports closing a window.

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/services/public/cpp/view_manager/lib/view_manager_synchronizer.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "mojo/public/cpp/application/connect.h"
 #include "mojo/public/interfaces/service_provider/service_provider.mojom.h"
@@ skipping 216 matching lines @@
  public:
   DestroyViewTreeNodeTransaction(TransportNodeId node_id,
                                  ViewManagerSynchronizer* synchronizer)
       : ViewManagerTransaction(TYPE_DESTROY_VIEW_TREE_NODE, synchronizer),
         node_id_(node_id) {}
   virtual ~DestroyViewTreeNodeTransaction() {}
 
  private:
   // Overridden from ViewManagerTransaction:
   virtual void DoCommit() OVERRIDE {
+    GetAndAdvanceNextServerChangeId();
     service()->DeleteNode(node_id_, ActionCompletedCallback());
   }
   virtual void DoActionCompleted(bool success) OVERRIDE {
     // TODO(beng): recovery?
   }
 
   const TransportNodeId node_id_;
   DISALLOW_COPY_AND_ASSIGN(DestroyViewTreeNodeTransaction);
 };
 
@@ skipping 424 matching lines @@
 void ViewManagerSynchronizer::RemoveFromPendingQueue(
     ViewManagerTransaction* transaction) {
   DCHECK_EQ(transaction, pending_transactions_.front());
   pending_transactions_.erase(pending_transactions_.begin());
   if (pending_transactions_.empty() && !changes_acked_callback_.is_null())
     changes_acked_callback_.Run();
 }
 
 }  // namespace view_manager
 }  // namespace mojo