chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/external_install_error.h

 // Copyright 2014 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_INSTALL_ERROR_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTERNAL_INSTALL_ERROR_H_
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
 #include "chrome/browser/extensions/webstore_data_fetcher_delegate.h"
 
 class Browser;
 class ExtensionInstallPromptShowParams;
-class ExtensionInstallUI;
 class GlobalError;
 class GlobalErrorService;
 
 namespace content {
 class BrowserContext;
 }
 
 namespace extensions {
 class Extension;
 class ExternalInstallManager;
@@ skipping 84 matching lines @@
   std::unique_ptr<WebstoreDataFetcher> webstore_data_fetcher_;
 
   base::WeakPtrFactory<ExternalInstallError> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalInstallError);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_INSTALL_ERROR_H_