Do not show the install prompt for themes.

chrome/browser/extensions/webstore_inline_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_WEBSTORE_INLINE_INSTALLER_H_
 #define CHROME_BROWSER_EXTENSIONS_WEBSTORE_INLINE_INSTALLER_H_
 #pragma once
 
 #include <string>
 
@@ skipping 96 matching lines @@
   // Checks whether the install is initiated by a page in the verified site
   // (which is at least a domain, but can also have a port or a path).
   static bool IsRequestorURLInVerifiedSite(const GURL& requestor_url,
                                            const std::string& verified_site);
 
   int install_id_;
   int return_route_id_;
   std::string id_;
   GURL requestor_url_;
   Delegate* delegate_;
+  scoped_ptr<ExtensionInstallUI> install_ui_;
 
   // For fetching webstore JSON data.
   scoped_ptr<content::URLFetcher> webstore_data_url_fetcher_;
 
   // Extracted from the webstore JSON data response.
   std::string localized_name_;
   std::string localized_description_;
   std::string localized_user_count_;
   double average_rating_;
   int rating_count_;
   scoped_ptr<DictionaryValue> webstore_data_;
   scoped_ptr<DictionaryValue> manifest_;
   scoped_refptr<Extension> dummy_extension_;
   SkBitmap icon_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(WebstoreInlineInstaller);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_WEBSTORE_INLINE_INSTALLER_H_