Put the RenderFrame's ID into a per-frame WebBluetooth, and plumb that back to the browser.

content/renderer/bluetooth/bluetooth_dispatcher.cc

 // Copyright 2014 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 "content/renderer/bluetooth/bluetooth_dispatcher.h"
 
 #include "base/lazy_instance.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/thread_task_runner_handle.h"
@@ skipping 131 matching lines @@
   IPC_MESSAGE_HANDLER(BluetoothMsg_WriteCharacteristicValueSuccess,
                       OnWriteValueSuccess);
   IPC_MESSAGE_HANDLER(BluetoothMsg_WriteCharacteristicValueError,
                       OnWriteValueError);
   IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   DCHECK(handled) << "Unhandled message:" << msg.type();
 }
 
 void BluetoothDispatcher::requestDevice(
+    int frame_routing_id,
     const WebRequestDeviceOptions& options,
     blink::WebBluetoothRequestDeviceCallbacks* callbacks) {
   int request_id = pending_requests_.Add(callbacks);
 
   // Convert |options| to its IPC form.
   std::vector<content::BluetoothScanFilter> filters(options.filters.size());
   for (size_t i = 0; i < options.filters.size(); ++i) {
     const WebBluetoothScanFilter& web_filter = options.filters[i];
     BluetoothScanFilter& filter = filters[i];
     filter.services.reserve(web_filter.services.size());
     for (const WebString& service : web_filter.services) {
       filter.services.push_back(device::BluetoothUUID(service.utf8()));
     }
   }
   std::vector<device::BluetoothUUID> optional_services;
   optional_services.reserve(options.optionalServices.size());
   for (const WebString& optional_service : options.optionalServices) {
     optional_services.push_back(device::BluetoothUUID(optional_service.utf8()));
   }
 
   Send(new BluetoothHostMsg_RequestDevice(CurrentWorkerId(), request_id,
-                                          filters, optional_services));
+                                          frame_routing_id, filters,
+                                          optional_services));
 }
 
 void BluetoothDispatcher::connectGATT(
     const blink::WebString& device_instance_id,
     blink::WebBluetoothConnectGATTCallbacks* callbacks) {
   int request_id = pending_connect_requests_.Add(callbacks);
   Send(new BluetoothHostMsg_ConnectGATT(CurrentWorkerId(), request_id,
                                         device_instance_id.utf8()));
 }
 
@@ skipping 194 matching lines @@
                                             WebBluetoothError error) {
   DCHECK(pending_write_value_requests_.Lookup(request_id)) << request_id;
 
   pending_write_value_requests_.Lookup(request_id)
       ->onError(new WebBluetoothError(error));
 
   pending_write_value_requests_.Remove(request_id);
 }
 
 }  // namespace content