Have LazyBackgroundTaskQueue notify consumers when the transient page fails to

chrome/browser/extensions/extension_message_service.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 108 matching lines @@
   // to open a channel. Returns true if a task was queued.
   bool MaybeAddPendingOpenChannelTask(Profile* profile,
                                       const OpenChannelParams& params);
 
   // Callbacks for LazyBackgroundTaskQueue tasks. The queue passes in an
   // ExtensionHost to its task callbacks, though some of our callbacks don't
   // use that argument.
   void PendingOpenChannel(const OpenChannelParams& params,
                           int source_process_id,
                           ExtensionHost* host);
-  void PendingCloseChannel(int port_id, bool connection_error, ExtensionHost*) {
-    CloseChannel(port_id, connection_error);
+  void PendingCloseChannel(int port_id,
+                           bool connection_error,
+                           ExtensionHost* host) {
+    if (host)
+      CloseChannel(port_id, connection_error);
   }
   void PendingPostMessage(int port_id,
                           const std::string& message,
-                          ExtensionHost*) {
-    PostMessageFromRenderer(port_id, message);
+                          ExtensionHost* host) {
+    if (host)
+      PostMessageFromRenderer(port_id, message);
   }
 
   content::NotificationRegistrar registrar_;
   MessageChannelMap channels_;
   PendingChannelMap pending_channels_;
 
   // Weak pointer. Guaranteed to outlive this class.
   extensions::LazyBackgroundTaskQueue* lazy_background_task_queue_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionMessageService);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_