Add webusb notification UI code

components/webusb/webusb_detector.cc

Index: components/webusb/webusb_detector.cc
diff --git a/components/webusb/webusb_detector.cc b/components/webusb/webusb_detector.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8829f97aabf0da141d5c248204bcad2d3d19bc70
--- /dev/null
+++ b/components/webusb/webusb_detector.cc
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+// 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 "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 {
+
+namespace {
+
+WebUsbDetector* webusb_detector = nullptr;
+
+}  // namespace
+
+WebUsbDetector::WebUsbDetector() : observer_(this) {
+  Initialize();
+}
+
+WebUsbDetector::~WebUsbDetector() {}
+
+WebUsbDetector* WebUsbDetector::Get() {
+  return webusb_detector;
+}
+
+void WebUsbDetector::Set(WebUsbDetector* detector) {
+  webusb_detector = detector;
+}
+
+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()) {

[stevenjb, 2015/08/27 16:56:02]

Where does webusb_landing_page come from, and is calling is_valid() sufficient?
I honestly don't know, I just want to make sure it has been run by the security
team. It might be good to add a comment so that other devs don't keep asking the
same question :)

[Reilly Grant (use Gerrit), 2015/08/27 17:03:00]

webusb_landing_page comes from the device. Let's look around to see if there's
some good URL sanitization code we use in other places to protect against
Javascript in URLs and such.

[juncai, 2015/08/27 19:58:39]

Done.

+    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