Making ShowExtensionInstallDialog a callback

chrome/browser/extensions/crx_installer.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_CRX_INSTALLER_H_
 #define CHROME_BROWSER_EXTENSIONS_CRX_INSTALLER_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 341 matching lines @@
 
   // Whether we should produce an error if the manifest declares requirements
   // that are not met. If false and there is an unmet requirement, the install
   // will continue but the extension will be distabled.
   bool error_on_unsupported_requirements_;
 
   scoped_ptr<RequirementsChecker> requirements_checker_;
 
   bool has_requirement_errors_;
 
+  // Used to show the install dialog.
+  ExtensionInstallPrompt::ShowDialogCallback show_dialog_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(CrxInstaller);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_CRX_INSTALLER_H_