[Media Device Management] Check if the interface is already bound.

While testing locally I have encountered and issue such that an
interface would be bound while already bound. This fixes that behavior
so that the related DCHECK is not triggered.

Similar issue and fix: http://crbug.com/817873#c7


Bug: 997661
Change-Id: Ifcd1342bd9cbf2c2895e5b7f2c1967c06b2a84d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1903197Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Armando Miraglia <armax@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713772}

third_party/blink/renderer/modules/mediastream/media_stream_device_observer.cc

@@ -135,6 +135,9 @@ void MediaStreamDeviceObserver::OnDeviceChanged(
 
 void MediaStreamDeviceObserver::BindMediaStreamDeviceObserverReceiver(
     mojo::PendingReceiver<mojom::blink::MediaStreamDeviceObserver> receiver) {
+  if (receiver_.is_bound())
+    return;
+
   receiver_.Bind(std::move(receiver));
 }