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

content/browser/bluetooth/bluetooth_dispatcher_host.h

Index: content/browser/bluetooth/bluetooth_dispatcher_host.h
diff --git a/content/browser/bluetooth/bluetooth_dispatcher_host.h b/content/browser/bluetooth/bluetooth_dispatcher_host.h
index c118d15f460e9a35b91f6bc3d92a8301ee94823c..fd79e5e737f642feae76fad73c520290ad2ba667 100644
--- a/content/browser/bluetooth/bluetooth_dispatcher_host.h
+++ b/content/browser/bluetooth/bluetooth_dispatcher_host.h
@@ -34,7 +34,7 @@ class CONTENT_EXPORT BluetoothDispatcherHost final
     : public BrowserMessageFilter,
       public device::BluetoothAdapter::Observer {
  public:
-  BluetoothDispatcherHost();
+  BluetoothDispatcherHost(int render_process_id);
   // BrowserMessageFilter:
   void OnDestruct() const override;
   void OverrideThreadForMessage(const IPC::Message& message,
@@ -61,6 +61,7 @@ class CONTENT_EXPORT BluetoothDispatcherHost final
   void OnRequestDevice(
       int thread_id,
       int request_id,
+      int frame_routing_id,
       const std::vector<content::BluetoothScanFilter>& filters,
       const std::vector<device::BluetoothUUID>& optional_services);
   void OnConnectGATT(int thread_id, int request_id,
@@ -133,6 +134,8 @@ class CONTENT_EXPORT BluetoothDispatcherHost final
                           int request_id,
                           device::BluetoothGattService::GattErrorCode);
 
+  int render_process_id_;
+
   // Maps a (thread_id,request_id) to information about its requestDevice call,
   // including the chooser dialog.
   // An entry is added to this map in OnRequestDevice, and should be removed