Mandoline: ConnectToApplication and ConnectToService should fail gracefully

mojo/application/public/cpp/lib/application_impl.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/application/public/cpp/application_impl.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 47 matching lines @@
 
 ApplicationImpl::~ApplicationImpl() {
   DCHECK(!in_destructor_);
   in_destructor_ = true;
   ClearConnections();
   app_lifetime_helper_.ApplicationTerminated();
 }
 
 ApplicationConnection* ApplicationImpl::ConnectToApplication(
     mojo::URLRequestPtr request) {
-  MOJO_CHECK(shell_);
+  if (!shell_)
+    return nullptr;
   ServiceProviderPtr local_services;
   InterfaceRequest<ServiceProvider> local_request = GetProxy(&local_services);
   ServiceProviderPtr remote_services;
   std::string application_url = request->url.To<std::string>();
   shell_->ConnectToApplication(request.Pass(), GetProxy(&remote_services),
                                local_services.Pass());
   internal::ServiceRegistry* registry = new internal::ServiceRegistry(
       this, application_url, application_url, remote_services.Pass(),
       local_request.Pass());
   if (!delegate_->ConfigureOutgoingConnection(registry)) {
@@ skipping 86 matching lines @@
 
 void ApplicationImpl::OnConnectionError() {
   base::WeakPtr<ApplicationImpl> ptr(weak_factory_.GetWeakPtr());
   QuitNow();
   if (!ptr)
     return;
   shell_ = nullptr;
 }
 
 }  // namespace mojo