bluetooth: Clean up WebBluetoothServiceImpl when adapter is removed

content/browser/bluetooth/bluetooth_dispatcher_host.cc

Index: content/browser/bluetooth/bluetooth_dispatcher_host.cc
diff --git a/content/browser/bluetooth/bluetooth_dispatcher_host.cc b/content/browser/bluetooth/bluetooth_dispatcher_host.cc
index 78d8c12391f6f614c079fccffdce789b86a95245..2c9a3eb4f04e2ef287131a7bb5c1b703a8290e1c 100644
--- a/content/browser/bluetooth/bluetooth_dispatcher_host.cc
+++ b/content/browser/bluetooth/bluetooth_dispatcher_host.cc
@@ -483,6 +483,12 @@ void BluetoothDispatcherHost::set_adapter(
     for (device::BluetoothAdapter::Observer* observer : adapter_observers_) {
       adapter_->AddObserver(observer);
     }
+  } else {
+    // Notify that the adapter has been removed and observers should clean up
+    // their state.
+    for (device::BluetoothAdapter::Observer* observer : adapter_observers_) {
+      observer->AdapterPresentChanged(nullptr, false);

[Jeffrey Yasskin, 2016/04/19 21:08:27]

To be strictly correct, this should probably pass the old adapter rather than
nullptr. It's not going to matter any time soon, because we don't deal with
having multiple adapters, but it might matter eventually. 

We should probably send this for every adapter change (with unequal pointers?)
so that notifications never hold dangling references to the old adapter, but I
like your ClearState() implementation, and that only works when changing the
adapter to null, so I endorse limiting the artificial AdapterPresentChange to
this subset of actual changes.

[ortuno, 2016/04/19 21:36:32]

In practice there will never be more than one adapter object, no matter how many
physical adapters the device has (BluetoothAdapter is actually a misnomer. It
doesn't represent a single physical adpater, it manages all adapters and allows
you to access whichever one is available). So this event always called with a
pointer to that adapter object.
Acknowledged.

+    }
   }
 }