Fix app_shell shutdown crash due to BrowserContextKeyedServices

chrome/browser/chromeos/drive/drive_integration_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_CHROMEOS_DRIVE_DRIVE_INTEGRATION_SERVICE_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_INTEGRATION_SERVICE_H_
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
@@ skipping 190 matching lines @@
   static DriveIntegrationService* FindForProfile(Profile* profile);
 
   // Same as FindForProfile. TODO(hidehiko): Remove this.
   static DriveIntegrationService* FindForProfileRegardlessOfStates(
       Profile* profile);
 
   // Returns the DriveIntegrationServiceFactory instance.
   static DriveIntegrationServiceFactory* GetInstance();
 
   // Sets a factory function for tests.
-  static void SetFactoryForTest(const FactoryCallback& factory_for_test);
+  // NOTE: Call SetFactoryForTest(NULL) during your test TearDown so you don't
+  // pollute the next test.
+  static void SetFactoryForTest(FactoryCallback* factory_for_test);

[xiyuan, 2014/01/09 17:53:22]

nit: How about making this private and use a
ScopedDriveIntegrationServiceFactoryForTest class to access it and automatically
clears it on destruction?

 
  private:
   friend struct DefaultSingletonTraits<DriveIntegrationServiceFactory>;
 
   DriveIntegrationServiceFactory();
   virtual ~DriveIntegrationServiceFactory();
 
   // BrowserContextKeyedServiceFactory:
   virtual BrowserContextKeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const OVERRIDE;
 
-  FactoryCallback factory_for_test_;
+  // This is static so it can be set without instantiating the factory. This
+  // allows factory creation to be delayed until it normally happens (on profile
+  // creation) rather than when tests are set up. DriveIntegrationServiceFactory
+  // transitively depends on ExtensionSystemFactory which crashes if created too
+  // soon (i.e. before the BrowserProcess exists).
+  static FactoryCallback* factory_for_test_;
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_INTEGRATION_SERVICE_H_