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

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 97ac8777aa2119dbcea544a38f485533535de511..a8047b6685984c3ffcf83665b4f417a81ab831a9 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -21,6 +21,7 @@
 #include "base/time/time.h"
 #include "cc/base/switches.h"
 #include "content/child/appcache/appcache_dispatcher.h"
+#include "content/child/bluetooth/web_bluetooth_impl.h"
 #include "content/child/permissions/permission_dispatcher.h"
 #include "content/child/plugin_messages.h"
 #include "content/child/quota_dispatcher.h"
@@ -3813,6 +3814,15 @@ void RenderFrameImpl::unregisterProtocolHandler(const WebString& scheme,
                                                   user_gesture));
 }
 
+blink::WebBluetooth* RenderFrameImpl::bluetooth() {
+  if (!bluetooth_) {
+    bluetooth_.reset(new WebBluetoothImpl(
+        ChildThreadImpl::current()->thread_safe_sender(), routing_id_));
+  }
+
+  return bluetooth_.get();
+}
+
 #if defined(ENABLE_WEBVR)
 blink::WebVRClient* RenderFrameImpl::webVRClient() {
   if (!vr_dispatcher_)