Fix crash when user closes window prior to the "Confirm Install" prompt showing

chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller.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_UI_COCOA_EXTENSIONS_EXTENSION_INSTALL_DIALOG_CONTROLER_H_
 #define CHROME_BROWSER_UI_COCOA_EXTENSIONS_EXTENSION_INSTALL_DIALOG_CONTROLER_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/scoped_nsobject.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_mac.h"
 
 namespace content {
 class PageNavigator;
 class WebContents;
 }
 
 namespace extensions {
 class ExperienceSamplingEvent;
 }
 
+class ExtensionInstallPromptShowParams;
 @class ExtensionInstallViewController;
 
 // Displays an extension install prompt as a tab modal dialog.
 class ExtensionInstallDialogController :
     public ExtensionInstallPrompt::Delegate,
     public ConstrainedWindowMacDelegate {
  public:
   ExtensionInstallDialogController(
-      const ExtensionInstallPrompt::ShowParams& show_params,
+      ExtensionInstallPromptShowParams* show_params,
       ExtensionInstallPrompt::Delegate* delegate,
       scoped_refptr<ExtensionInstallPrompt::Prompt> prompt);
   ~ExtensionInstallDialogController() override;
 
   // ExtensionInstallPrompt::Delegate implementation.
   void InstallUIProceed() override;
   void InstallUIAbort(bool user_initiated) override;
 
   // ConstrainedWindowMacDelegate implementation.
   void OnConstrainedWindowClosed(ConstrainedWindowMac* window) override;
 
   ConstrainedWindowMac* constrained_window() const {
     return constrained_window_.get();
   }
   ExtensionInstallViewController* view_controller() const {
     return view_controller_;
   }
 
  private:
   ExtensionInstallPrompt::Delegate* delegate_;
   base::scoped_nsobject<ExtensionInstallViewController> view_controller_;
   scoped_ptr<ConstrainedWindowMac> constrained_window_;
   scoped_ptr<extensions::ExperienceSamplingEvent> sampling_event_;
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_EXTENSIONS_EXTENSION_INSTALL_DIALOG_CONTROLLER_H_