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

content/browser/renderer_host/render_process_host_impl.cc

 // Copyright 2012 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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 912 matching lines @@
     AddFilter(new MemoryBenchmarkMessageFilter());
 #endif
   AddFilter(new PushMessagingMessageFilter(
       GetID(), storage_partition_impl_->GetServiceWorkerContext()));
 #if defined(OS_ANDROID)
   AddFilter(new ScreenOrientationMessageFilterAndroid());
 #endif
   AddFilter(new GeofencingDispatcherHost(
       storage_partition_impl_->GetGeofencingManager()));
   if (browser_command_line.HasSwitch(switches::kEnableWebBluetooth)) {
-    bluetooth_dispatcher_host_ = new BluetoothDispatcherHost();
+    bluetooth_dispatcher_host_ = new BluetoothDispatcherHost(GetID());
     AddFilter(bluetooth_dispatcher_host_.get());
   }
 }
 
 void RenderProcessHostImpl::RegisterMojoServices() {
   mojo_application_host_->service_registry()->AddService(
       base::Bind(&device::BatteryMonitorImpl::Create));
 
   mojo_application_host_->service_registry()->AddService(
       base::Bind(&device::VibrationManagerImpl::Create));
@@ skipping 1566 matching lines @@
 void RenderProcessHostImpl::GetAudioOutputControllers(
     const GetAudioOutputControllersCallback& callback) const {
   audio_renderer_host()->GetOutputControllers(callback);
 }
 
 BluetoothDispatcherHost* RenderProcessHostImpl::GetBluetoothDispatcherHost() {
   return bluetooth_dispatcher_host_.get();
 }
 
 }  // namespace content