bluetooth: Improve error message for retrieving Descriptors when disconnecting

third_party/WebKit/LayoutTests/bluetooth/script-tests/characteristic/descriptor-device-disconnects-during-success.js

+'use strict';
+promise_test(
+    () => {
+      let val = new Uint8Array([1]);
+      return setBluetoothFakeAdapter('DisconnectingHealthThermometerAdapter')
+          .then(() => requestDeviceWithKeyDown({
+                  filters: [{services: ['health_thermometer']}],
+                  optionalServices: [request_disconnection_service_uuid]
+                }))
+          .then(device => device.gatt.connect())
+          .then(gattServer => {
+            let measurement_interval;
+            return gattServer.getPrimaryService('health_thermometer')
+                .then(ht => ht.getCharacteristic('measurement_interval'))
+                .then(mi => measurement_interval = mi)
+                .then(() => get_request_disconnection(gattServer))
+                .then(requestDisconnection => {
+                  requestDisconnection();
+                  return assert_promise_rejects_with_message(
+                      measurement_interval.CALLS(
+                          [getDescriptor(user_description.name) |
+                           getDescriptors(user_description.name)[UUID] |
+                           getDescriptors()]),
+                      new DOMException(
+                          'GATT Server is disconnected. Cannot retrieve descriptors. ' +
+                              '(Re)connect first with `device.gatt.connect`.',
+                          'NetworkError'));
+                });
+          });
+    },
+    'Device disconnects during a FUNCTION_NAME call that succeeds. ' +
+        'Reject with NetworkError.');