Fixes crash in view_manager_lib

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 429 matching lines @@
 ViewManagerSynchronizer::ViewManagerSynchronizer(ViewManagerDelegate* delegate)
     : view_manager_(new ViewManager(this, delegate)),
       connected_(false),
       connection_id_(0),
       next_id_(1),
       next_server_change_id_(0),
       sync_factory_(this) {
 }
 
 ViewManagerSynchronizer::~ViewManagerSynchronizer() {
+  // Destroying the |view_manager_| may attempt to add transactions to
+  // |pending_transactions_|. So we need to destroy |view_manager_| first.
+  view_manager_.reset();
 }
 
 TransportNodeId ViewManagerSynchronizer::CreateViewTreeNode() {
   DCHECK(connected_);
   const TransportNodeId node_id(
       MakeTransportId(connection_id_, ++next_id_));
   pending_transactions_.push_back(
       new CreateViewTreeNodeTransaction(node_id, this));
   Sync();
   return node_id;
@@ skipping 209 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