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

content/child/bluetooth/web_bluetooth_impl.cc

Index: content/child/bluetooth/web_bluetooth_impl.cc
diff --git a/content/child/bluetooth/web_bluetooth_impl.cc b/content/child/bluetooth/web_bluetooth_impl.cc
index c307461a5345fe98d311dd38defbf9fbe3c55ba8..166018ec23a1304a7e01f2df3f2f17ee9db9598e 100644
--- a/content/child/bluetooth/web_bluetooth_impl.cc
+++ b/content/child/bluetooth/web_bluetooth_impl.cc
@@ -6,11 +6,18 @@
 
 #include "content/child/bluetooth/bluetooth_dispatcher.h"
 #include "content/child/thread_safe_sender.h"
+#include "ipc/ipc_message.h"
 
 namespace content {
 
 WebBluetoothImpl::WebBluetoothImpl(ThreadSafeSender* thread_safe_sender)
-    : thread_safe_sender_(thread_safe_sender) {
+    : WebBluetoothImpl(thread_safe_sender, MSG_ROUTING_NONE) {
+}
+
+WebBluetoothImpl::WebBluetoothImpl(ThreadSafeSender* thread_safe_sender,
+                                   int frame_routing_id)
+    : thread_safe_sender_(thread_safe_sender),
+      frame_routing_id_(frame_routing_id) {

[jochen (gone - plz use gerrit), 2015/07/15 13:40:55]

stuff in child/ shouldn't know about frames.

why is bluetooth in child/ anyway, does anything but renderer use it?

[Jeffrey Yasskin, 2015/07/15 15:47:16]

Would this be better if I called it a "routing_id" instead of a
"frame_routing_id"? The code in child/ isn't using frames in any way; it's just
propagating an ID back to the browser. There's a bunch of instances of code in
content/child and content/common using routing_ids.
Right now, Web Bluetooth is only exposed on window.navigator, and not in
Workers, but we anticipate most of the API eventually being accessible to
Workers and wanted to architect the code to make sure that's straightforward.
The one part that *won't* be accessible is requestDevice(), since that needs to
be called from a Window in order to show its chooser dialog. But it seemed like
overkill to add a whole extra interface in content/renderer to handle that one
function.

 }
 
 WebBluetoothImpl::~WebBluetoothImpl() {
@@ -19,7 +26,7 @@ WebBluetoothImpl::~WebBluetoothImpl() {
 void WebBluetoothImpl::requestDevice(
     const blink::WebRequestDeviceOptions& options,
     blink::WebBluetoothRequestDeviceCallbacks* callbacks) {
-  GetDispatcher()->requestDevice(options, callbacks);
+  GetDispatcher()->requestDevice(frame_routing_id_, options, callbacks);
 }
 
 void WebBluetoothImpl::connectGATT(const blink::WebString& device_instance_id,