[Extensions] DCHECK that ExtensionFunctions respond (and only once)

chrome/browser/chromeos/file_manager/file_manager_browsertest_base.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 "chrome/browser/chromeos/file_manager/file_manager_browsertest_base.h"
 
 #include <stddef.h>
 
 #include <deque>
 
@@ skipping 211 matching lines @@
   }
 
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override {
     Message entry;
     entry.type = type;
     entry.message = type != extensions::NOTIFICATION_EXTENSION_TEST_PASSED
                         ? *content::Details<std::string>(details).ptr()
                         : std::string();
-    entry.function =
-        type == extensions::NOTIFICATION_EXTENSION_TEST_MESSAGE
-            ? content::Source<extensions::TestSendMessageFunction>(source).ptr()
-            : NULL;
+    if (type == extensions::NOTIFICATION_EXTENSION_TEST_MESSAGE) {
+      entry.function =
+          content::Source<extensions::TestSendMessageFunction>(source).ptr();
+      *content::Details<std::pair<std::string, bool*>>(details).ptr()->second =
+          true;
+    }
     messages_.push_back(entry);
     base::MessageLoopForUI::current()->QuitWhenIdle();
   }
 
  private:
   std::deque<Message> messages_;
   content::NotificationRegistrar registrar_;
 };
 
 }  // anonymous namespace
@@ skipping 331 matching lines @@
     }
 
     // Parse the message value as JSON.
     const std::unique_ptr<const base::Value> value =
         base::JSONReader::Read(entry.message);
 
     // If the message is not the expected format, just ignore it.
     const base::DictionaryValue* message_dictionary = NULL;
     std::string name;
     if (!value || !value->GetAsDictionary(&message_dictionary) ||
-        !message_dictionary->GetString("name", &name))
+        !message_dictionary->GetString("name", &name)) {
+      entry.function->Reply(std::string());
       continue;
+    }
 
     std::string output;
     OnMessage(name, *message_dictionary, &output);
     if (HasFatalFailure())
       break;
 
     entry.function->Reply(output);
   }
 }
 
@@ skipping 127 matching lines @@
 }
 
 drive::DriveIntegrationService*
 FileManagerBrowserTestBase::CreateDriveIntegrationService(Profile* profile) {
   drive_volumes_[profile->GetOriginalProfile()].reset(new DriveTestVolume());
   return drive_volumes_[profile->GetOriginalProfile()]
       ->CreateDriveIntegrationService(profile);
 }
 
 }  // namespace file_manager