Add webusb notification UI code

components/webusb/webusb_browser_client.h

+// Copyright 2015 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 COMPONENTS_WEBUSB_WEBUSB_BROWSER_CLIENT_H_
+#define COMPONENTS_WEBUSB_WEBUSB_BROWSER_CLIENT_H_
+
+#include "base/macros.h"
+
+class GURL;
+
+namespace webusb {
+
+// Interface to allow the webusb module to make browser-process-specific
+// calls. Should be Set() once in the browser process.
+
+class WebUsbBrowserClient {
+ public:
+  virtual ~WebUsbBrowserClient() {}
+
+  virtual void OpenURL(const GURL& url) = 0;
+
+  virtual bool WebUsbNotificationEnabled() = 0;
+
+  // Returns the single instance of |this|.
+  static WebUsbBrowserClient* Get();
+
+  // Initialize the single instance.
+  static void Set(WebUsbBrowserClient* client);
+};
+
+}  // namespace webusb
+
+#endif  // COMPONENTS_WEBUSB_WEBUSB_BROWSER_CLIENT_H_