Disable install of new default_apps for existing users

chrome/browser/extensions/default_apps.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_DEFAULT_APPS_H_
 #define CHROME_BROWSER_EXTENSIONS_DEFAULT_APPS_H_
 
 #include "base/basictypes.h"
 #include "chrome/browser/extensions/external_provider_impl.h"
 
@@ skipping 14 matching lines @@
   // Now unused, left for backward compatibility.
   kProvideLegacyDefaultApps,
   kNeverInstallDefaultApps,
   kAlreadyInstalledDefaultApps
 };
 
 bool ShouldInstallInProfile(Profile* profile);
 
 bool isLocaleSupported();
 
+extern bool isMigration;
+
 // Register preference properties used by default apps to maintain
 // install state.
 void RegisterUserPrefs(PrefService* prefs);
 
 // A specialization of the ExternalProviderImpl that conditionally installs apps
 // from the chrome::DIR_DEFAULT_APPS location based on a preference in the
 // profile.
 class Provider : public extensions::ExternalProviderImpl {
  public:
   Provider(Profile* profile,
            VisitorInterface* service,
            extensions::ExternalLoader* loader,
            extensions::Extension::Location crx_location,
            extensions::Extension::Location download_location,
            int creation_flags);
 
   // ExternalProviderImpl overrides:
   virtual void VisitRegisteredExtension() OVERRIDE;
 
  private:
   Profile* profile_;
 
   DISALLOW_COPY_AND_ASSIGN(Provider);
 };
 
 }  // namespace default_apps
 
 #endif  // CHROME_BROWSER_EXTENSIONS_DEFAULT_APPS_H_