Add message and Help Center link to the chooser UI

chrome/browser/usb/usb_chooser_bubble_delegate.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 "chrome/browser/usb/usb_chooser_bubble_delegate.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/usb/usb_chooser_context.h"
 #include "chrome/browser/usb/usb_chooser_context_factory.h"
+#include "chrome/common/url_constants.h"
 #include "components/bubble/bubble_controller.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents.h"
 #include "device/core/device_client.h"
 #include "device/usb/mojo/type_converters.h"
 #include "device/usb/usb_device.h"
 #include "device/usb/usb_device_filter.h"
 #include "url/gurl.h"
 
 namespace {
@@ skipping 128 matching lines @@
   if (device::UsbDeviceFilter::MatchesAny(device, filters_) &&
       FindInAllowedOrigins(
           device->webusb_allowed_origins(),
           render_frame_host_->GetLastCommittedURL().GetOrigin())) {
     devices_.push_back(std::make_pair(device, device->product_string()));
     if (observer())
       observer()->OnOptionAdded(devices_.size() - 1);
   }
 }
 
+GURL UsbChooserBubbleDelegate::GetHelpCenterURL() const {
+  return GURL(chrome::kWebUsbHelpCenterURL);

[msw, 2016/02/17 01:31:35]

Does it make sense to link to a general support url for now?

[juncai, 2016/02/17 22:40:40]

A WebUsb help center URL has been requested, once the URL is available, I will
change it to that URL. I filed a bug to track it:
https://crbug.com/587525

+}
+
 void UsbChooserBubbleDelegate::OnDeviceRemoved(
     scoped_refptr<device::UsbDevice> device) {
   for (auto it = devices_.begin(); it != devices_.end(); ++it) {
     if (it->first == device) {
       size_t index = it - devices_.begin();
       devices_.erase(it);
       if (observer())
         observer()->OnOptionRemoved(index);
       return;
     }
@@ skipping 13 matching lines @@
     }
   }
   if (observer())
     observer()->OnOptionsInitialized();
 }
 
 void UsbChooserBubbleDelegate::set_bubble_controller(
     BubbleReference bubble_controller) {
   bubble_controller_ = bubble_controller;
 }