Do not show the install prompt for themes.

chrome/browser/extensions/extension_webstore_private_api.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_EXTENSION_WEBSTORE_PRIVATE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_WEBSTORE_PRIVATE_API_H_
 #pragma once
 
 #include <string>
 
@@ skipping 122 matching lines @@
   bool use_app_installed_bubble_;
 
   // The results of parsing manifest_ and icon_data_ go into these two.
   scoped_ptr<base::DictionaryValue> parsed_manifest_;
   SkBitmap icon_;
 
   // A dummy Extension object we create for the purposes of using
   // ExtensionInstallUI to prompt for confirmation of the install.
   scoped_refptr<Extension> dummy_extension_;
 
+  // The class that displays the install prompt.
+  scoped_ptr<ExtensionInstallUI> install_ui_;
+
   DECLARE_EXTENSION_FUNCTION_NAME("webstorePrivate.beginInstallWithManifest3");
 };
 
 class CompleteInstallFunction : public SyncExtensionFunction {
   virtual bool RunImpl() OVERRIDE;
   DECLARE_EXTENSION_FUNCTION_NAME("webstorePrivate.completeInstall");
 };
 
 class SilentlyInstallFunction : public AsyncExtensionFunction,
                                 public WebstoreInstallHelper::Delegate,
@@ skipping 57 matching lines @@
   void CreateResult(bool webgl_allowed);
 
   // A false return value is always valid, but a true one is only valid if full
   // GPU info has been collected in a GPU process.
   static bool IsWebGLAllowed(content::GpuDataManager* manager);
 
   DECLARE_EXTENSION_FUNCTION_NAME("webstorePrivate.getWebGLStatus");
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_WEBSTORE_PRIVATE_API_H_