Add a chrome://webapks page.

chrome/browser/ui/webui/webapks_ui.h

+// Copyright 2017 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_WEBAPKS_UI_H_
+#define CHROME_BROWSER_UI_WEBUI_WEBAPKS_UI_H_
+
+#include "base/macros.h"
+#include "content/public/browser/web_ui_controller.h"
+
+// The WebUI handler for chrome://webapks.
+class WebApksUI : public content::WebUIController {
+ public:
+  explicit WebApksUI(content::WebUI* web_ui);
+  ~WebApksUI() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(WebApksUI);
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_WEBAPKS_UI_H_