Add message and Help Center link to the chooser UI

chrome/browser/usb/usb_chooser_bubble_delegate.cc

Index: chrome/browser/usb/usb_chooser_bubble_delegate.cc
diff --git a/chrome/browser/usb/usb_chooser_bubble_delegate.cc b/chrome/browser/usb/usb_chooser_bubble_delegate.cc
index 61549c4f8dbe425a05dbc94acd064dd0a79d1260..d7850e38f80b80c3278adff9e21d929af5713976 100644
--- a/chrome/browser/usb/usb_chooser_bubble_delegate.cc
+++ b/chrome/browser/usb/usb_chooser_bubble_delegate.cc
@@ -10,9 +10,11 @@
 #include "base/bind.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
+#include "base/strings/utf_string_conversions.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"
@@ -20,7 +22,6 @@
 #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 {
 
@@ -161,6 +162,10 @@ void UsbChooserBubbleDelegate::OnDeviceAdded(
   }
 }
 
+base::string16 UsbChooserBubbleDelegate::GetHelpCenterUrl() const {
+  return base::ASCIIToUTF16(chrome::kChooserUsbOverviewURL);
+}
+
 void UsbChooserBubbleDelegate::OnDeviceRemoved(
     scoped_refptr<device::UsbDevice> device) {
   for (auto it = devices_.begin(); it != devices_.end(); ++it) {