Mojo C++ bindings: handle double peer endpoint closed event for the same endpoint.

mojo/public/cpp/bindings/lib/multiplex_router.cc

 // Copyright 2015 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/public/cpp/bindings/lib/multiplex_router.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 508 matching lines @@
   return true;
 }
 
 bool MultiplexRouter::OnPeerAssociatedEndpointClosed(InterfaceId id) {
   lock_.AssertAcquired();
 
   if (IsMasterInterfaceId(id))
     return false;
 
   InterfaceEndpoint* endpoint = FindOrInsertEndpoint(id, nullptr);
-  DCHECK(!endpoint->peer_closed());
 
-  if (endpoint->client())
-    tasks_.push_back(Task::CreateNotifyErrorTask(endpoint));
-  UpdateEndpointStateMayRemove(endpoint, PEER_ENDPOINT_CLOSED);
+  // It is possible that this endpoint has been set as peer closed. That is
+  // because when the message pipe is closed, all the endpoints are updated with
+  // PEER_ENDPOINT_CLOSED. We continue to process remaining tasks in the queue,
+  // as long as there are refs keeping the router alive. If there is a
+  // PeerAssociatedEndpointClosedEvent control message in the queue, we will get
+  // here and see that the endpoint has been marked as peer closed.
+  if (!endpoint->peer_closed()) {
+    if (endpoint->client())
+      tasks_.push_back(Task::CreateNotifyErrorTask(endpoint));
+    UpdateEndpointStateMayRemove(endpoint, PEER_ENDPOINT_CLOSED);
+  }
 
   // No need to trigger a ProcessTasks() because it is already on the stack.
 
   return true;
 }
 
 bool MultiplexRouter::OnAssociatedEndpointClosedBeforeSent(InterfaceId id) {
   lock_.AssertAcquired();
 
   if (IsMasterInterfaceId(id))
@@ skipping 284 matching lines @@
       *inserted = true;
   } else {
     endpoint = iter->second.get();
   }
 
   return endpoint;
 }
 
 }  // namespace internal
 }  // namespace mojo