Remove unused WebUI extension files.

chrome/browser/ui/webui/extensions/extension_info_ui.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_WEBUI_EXTENSIONS_EXTENSION_INFO_UI_H_
-#define CHROME_BROWSER_UI_WEBUI_EXTENSIONS_EXTENSION_INFO_UI_H_
-
-#include "content/public/browser/web_ui_controller.h"
-#include "url/gurl.h"
-
-
-namespace base {
-class ListValue;
-}
-
-namespace content {
-class WebUIDataSource;
-}
-
-namespace extensions {
-
-// WebUI controller for the informative bubble shown on clicking a script badge.
-class ExtensionInfoUI : public content::WebUIController {
- public:
-  explicit ExtensionInfoUI(content::WebUI* web_ui, const GURL& url);
-
-  // Returns the chrome://extension-info/ URL for this extension.
-  static GURL GetURL(const std::string& extension_id);
-
- private:
-  ~ExtensionInfoUI() override;
-
-  // Load details about the extension into source_. Called during construction.
-  void AddExtensionDataToSource(const std::string& extension_id);
-
-  content::WebUIDataSource* source_;
-
-  DISALLOW_COPY_AND_ASSIGN(ExtensionInfoUI);
-};
-
-}  // namespace extensions
-
-#endif  // CHROME_BROWSER_UI_WEBUI_EXTENSIONS_EXTENSION_INFO_UI_H_