bluetooth: Improve GATT disconnected error message.

third_party/WebKit/LayoutTests/bluetooth/script-tests/server/device-disconnects-before.js

 'use strict';
 promise_test(t => {
   return setBluetoothFakeAdapter('DisconnectingHeartRateAdapter')
-    .then(() => requestDeviceWithKeyDown({
-      filters: [{services: ['heart_rate']}],
-      optionalServices: [request_disconnection_service_uuid]
-    }))
-    .then(device => {
-      return device.gatt.connect()
-        .then(gattServer => get_request_disconnection(gattServer))
-        .then(requestDisconnection => requestDisconnection())
-        .then(() => assert_promise_rejects_with_message(
-          device.gatt.CALLS([
-            getPrimaryService('heart_rate')|
-            getPrimaryServices()|
-            getPrimaryServices('heart_rate')[UUID]]),
-          new DOMException(
-            'GATT Server is disconnected. Cannot retrieve services.',
-            'NetworkError')));
-    });
+      .then(() => requestDeviceWithKeyDown({
+              filters: [{services: ['heart_rate']}],
+              optionalServices: [request_disconnection_service_uuid]
+            }))
+      .then(device => {
+        return device.gatt.connect()
+            .then(gattServer => get_request_disconnection(gattServer))
+            .then(requestDisconnection => requestDisconnection())
+            .then(
+                () => assert_promise_rejects_with_message(
+                    device.gatt.CALLS(
+                        [getPrimaryService('heart_rate') |
+                         getPrimaryServices() |
+                         getPrimaryServices('heart_rate')[UUID]]),
+                    new DOMException(
+                        'GATT Server is disconnected. ' +
+                            'Cannot retrieve services. ' +
+                            '(Re)connect first with `device.gatt.connect`.',
+                        'NetworkError')));
+      });
 }, 'Device disconnects before FUNCTION_NAME. Reject with NetworkError.');