Add a chrome://webapks page.

chrome/browser/ui/webui/webapks_handler.h

Index: chrome/browser/ui/webui/webapks_handler.h
diff --git a/chrome/browser/ui/webui/webapks_handler.h b/chrome/browser/ui/webui/webapks_handler.h
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+// 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_HANDLER_H_
+#define CHROME_BROWSER_UI_WEBUI_WEBAPKS_HANDLER_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "chrome/browser/android/webapk/webapk_info.h"
+#include "content/public/browser/web_ui_message_handler.h"
+
+namespace base {
+class ListValue;
+}  // namespace base
+
+// Handles JavaScript messages from the chrome://webapks page.
+class WebApksHandler : public content::WebUIMessageHandler {
+ public:
+  WebApksHandler();
+  ~WebApksHandler() override;
+
+  // content::WebUIMessageHandler:
+  void RegisterMessages() override;
+
+  // Handler for the "requestWebApksInfo" message. This requests
+  // information for the installed WebAPKs and returns it to JS using
+  // OnWebApkInfoReceived().
+  virtual void HandleRequestWebApksInfo(const base::ListValue* args);
+
+ private:
+  // Sends information for the installed WebAPKs to JS.
+  void OnWebApkInfoRetrieved(const std::vector<WebApkInfo>& webapks_list);
+
+  // Factory for the creating refs in callbacks.
+  base::WeakPtrFactory<WebApksHandler> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebApksHandler);
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_WEBAPKS_HANDLER_H_