Disable install of new default_apps for existing users

chrome/browser/extensions/external_provider_impl.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_EXTERNAL_PROVIDER_IMPL_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTERNAL_PROVIDER_IMPL_H_
 
 #include <string>
 
 #include "chrome/browser/extensions/external_provider_interface.h"
@@ skipping 34 matching lines @@
   virtual ~ExternalProviderImpl();
 
   // Populates a list with providers for all known sources.
   static void CreateExternalProviders(
       VisitorInterface* service,
       Profile* profile,
       ProviderCollection* provider_list);
 
   // Sets underlying prefs and notifies provider. Only to be called by the
   // owned ExternalLoader instance.
-  void SetPrefs(base::DictionaryValue* prefs);
+  virtual void SetPrefs(base::DictionaryValue* prefs);
 
   // ExternalProvider implementation:
   virtual void ServiceShutdown() OVERRIDE;
   virtual void VisitRegisteredExtension() OVERRIDE;
   virtual bool HasExtension(const std::string& id) const OVERRIDE;
   virtual bool GetExtensionDetails(const std::string& id,
                                    Extension::Location* location,
                                    scoped_ptr<Version>* version) const OVERRIDE;
 
   virtual bool IsReady() const OVERRIDE;
@@ skipping 39 matching lines @@
   // Whether loaded extensions should be automatically acknowledged, so that
   // the user doesn't see an alert about them.
   bool auto_acknowledge_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalProviderImpl);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_PROVIDER_IMPL_H_