Add message and Help Center link to the chooser UI

chrome/browser/usb/usb_chooser_bubble_delegate.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 CHROME_BROWSER_USB_USB_CHOOSER_BUBBLE_DELEGATE_H_
 #define CHROME_BROWSER_USB_USB_CHOOSER_BUBBLE_DELEGATE_H_
 
 #include <utility>
 
 #include "base/macros.h"
@@ skipping 27 matching lines @@
       content::RenderFrameHost* render_frame_host,
       const webusb::WebUsbPermissionBubble::GetPermissionCallback& callback);
   ~UsbChooserBubbleDelegate() override;
 
   // ChooserBubbleDelegate:
   size_t NumOptions() const override;
   const base::string16& GetOption(size_t index) const override;
   void Select(size_t index) override;
   void Cancel() override;
   void Close() override;
+  GURL GetHelpCenterUrl() const override;
 
   // device::UsbService::Observer:
   void OnDeviceAdded(scoped_refptr<device::UsbDevice> device) override;
   void OnDeviceRemoved(scoped_refptr<device::UsbDevice> device) override;
 
   void GotUsbDeviceList(
       const std::vector<scoped_refptr<device::UsbDevice>>& devices);
 
   void set_bubble_controller(BubbleReference bubble_controller);
 
  private:
   content::RenderFrameHost* const render_frame_host_;
   webusb::WebUsbPermissionBubble::GetPermissionCallback callback_;
   ScopedObserver<device::UsbService, device::UsbService::Observer>
       usb_service_observer_;
   std::vector<device::UsbDeviceFilter> filters_;
   // Each pair is a (device, device name).
   std::vector<std::pair<scoped_refptr<device::UsbDevice>, base::string16>>
       devices_;
   BubbleReference bubble_controller_;
   base::WeakPtrFactory<UsbChooserBubbleDelegate> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbChooserBubbleDelegate);
 };
 
 #endif  // CHROME_BROWSER_USB_USB_CHOOSER_BUBBLE_DELEGATE_H_