bluetooth: Introduce helper function for requesting a disconnection

third_party/WebKit/LayoutTests/bluetooth/connect/connect-disconnected-connect.html

Index: third_party/WebKit/LayoutTests/bluetooth/connect/connect-disconnected-connect.html
diff --git a/third_party/WebKit/LayoutTests/bluetooth/connect/connect-disconnected-connect.html b/third_party/WebKit/LayoutTests/bluetooth/connect/connect-disconnected-connect.html
index 84cee43ce4faf0731a7567761c55fcdf6a129cac..a3d239f67bdf16528e2a3bd97ae0679fadb3bed3 100644
--- a/third_party/WebKit/LayoutTests/bluetooth/connect/connect-disconnected-connect.html
+++ b/third_party/WebKit/LayoutTests/bluetooth/connect/connect-disconnected-connect.html
@@ -12,12 +12,11 @@
     }))
     .then(device => {
       return device.gatt.connect()
-        .then(gattServer => gattServer.getPrimaryService(request_disconnection_service_uuid))
-        .then(service => service.getCharacteristic(request_disconnection_characteristic_uuid))
+        .then(gattServer => get_request_disconnection(gattServer))
         .then(requestDisconnection => {
           let disconnected = eventPromise(device, 'gattserverdisconnected');
           // This write causes the device to disconnect.
-          return Promise.all([requestDisconnection.writeValue(new Uint8Array([0])),
+          return Promise.all([requestDisconnection(),
                               disconnected]);
         }).then(() => {
           return device.gatt.connect()