Add webusb notification UI code

components/webusb/webusb_detector.cc

+// 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.
+
+#include "components/webusb/webusb_detector.h"
+
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/singleton.h"
+#include "components/webusb/webusb_browser_client.h"
+#include "device/core/device_client.h"
+#include "device/usb/usb_device.h"
+#include "device/usb/usb_ids.h"
+
+namespace webusb {
+
+WebUsbDetector* WebUsbDetector::GetInstance() {
+  return Singleton<WebUsbDetector>::get();

[Reilly Grant (use Gerrit), 2015/08/26 22:32:12]

Issues I've been trying to resolve recently have convinced me that using globals
to define singletons makes it difficult to write tests as the singleton won't be
cleaned up between tests. Please make the WebUsbDetector simply owned by the
Chrome browser process like the WebUsbBrowserClient is.

[juncai, 2015/08/27 00:54:42]

Done.

+}
+
+WebUsbDetector::WebUsbDetector() : observer_(this) {
+  Initialize();
+}
+
+WebUsbDetector::~WebUsbDetector() {}
+
+void WebUsbDetector::Initialize() {
+  if (!webusb::WebUsbBrowserClient::Get()) {
+    return;
+  }
+
+  device::UsbService* usb_service =
+      device::DeviceClient::Get()->GetUsbService();
+  if (!usb_service)
+    return;
+
+  observer_.Add(usb_service);
+}
+
+void WebUsbDetector::OnDeviceAdded(scoped_refptr<device::UsbDevice> device) {
+  const base::string16& product_name = device->product_string();
+  if (product_name.empty()) {
+    return;
+  }
+
+  const GURL& landing_page = device->webusb_landing_page();
+  if (!landing_page.is_valid()) {
+    return;
+  }
+
+  std::string notification_id = device->guid();
+
+  webusb::WebUsbBrowserClient::Get()->OnDeviceAdded(product_name, landing_page,
+                                                    notification_id);
+}
+
+void WebUsbDetector::OnDeviceRemoved(scoped_refptr<device::UsbDevice> device) {
+  std::string notification_id = device->guid();
+  webusb::WebUsbBrowserClient::Get()->OnDeviceRemoved(notification_id);
+}
+
+}  // namespace webusb