Add UMA for the number of devices in the chooser when a device is paired

extensions/browser/app_window/app_window.h

Index: extensions/browser/app_window/app_window.h
diff --git a/extensions/browser/app_window/app_window.h b/extensions/browser/app_window/app_window.h
index 66fdd4c1417d283093f447fb63943f384f6577b0..26721ddb31f436dc3531d1f48f21fa73cf44d85f 100644
--- a/extensions/browser/app_window/app_window.h
+++ b/extensions/browser/app_window/app_window.h
@@ -435,7 +435,8 @@ class AppWindow : public content::WebContentsDelegate,
                              const blink::WebGestureEvent& event) override;
   std::unique_ptr<content::BluetoothChooser> RunBluetoothChooser(
       content::RenderFrameHost* frame,
-      const content::BluetoothChooser::EventHandler& event_handler) override;
+      const content::BluetoothChooser::EventHandler& event_handler,
+      bool accept_all_devices) override;
 
   // content::WebContentsObserver implementation.
   void RenderViewCreated(content::RenderViewHost* render_view_host) override;