Handle brokered attachment race condition

ipc/attachment_broker.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 "ipc/attachment_broker.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 40 matching lines @@
   auto it = std::find_if(observers_.begin(), observers_.end(),
                       [observer](const ObserverInfo& info) {
                         return info.observer == observer;
                       });
   if (it == observers_.end()) {
     ObserverInfo info;
     info.observer = observer;
     info.runner = runner;
     info.unique_id = ++last_unique_id_;
     observers_.push_back(info);
+
+    // Give the observer a chance to handle attachments that arrived while the
+    // observer was handling the message that caused it to register, but our
+    // mutex was not yet locked.
+    for (const auto& attachment : attachments_) {
+      info.runner->PostTask(
+          FROM_HERE,
+          base::Bind(&AttachmentBroker::NotifyObserver, base::Unretained(this),
+                     info.unique_id, attachment->GetIdentifier()));
+    }
   }
 }
 
 void AttachmentBroker::RemoveObserver(AttachmentBroker::Observer* observer) {
   base::AutoLock auto_lock(*get_lock());
   auto it = std::find_if(observers_.begin(), observers_.end(),
                       [observer](const ObserverInfo& info) {
                         return info.observer == observer;
                       });
   if (it != observers_.end())
@@ skipping 65 matching lines @@
 
   observer->ReceivedBrokerableAttachmentWithId(id);
 }
 
 AttachmentBroker::ObserverInfo::ObserverInfo() {}
 AttachmentBroker::ObserverInfo::ObserverInfo(const ObserverInfo& other) =
     default;
 AttachmentBroker::ObserverInfo::~ObserverInfo() {}
 
 }  // namespace IPC