bluetooth: Remove callback from BluetoothGattConnection::Disconnect

chrome/test/data/extensions/api_test/bluetooth_low_energy/connect_in_progress/runtest.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 var deviceAddress0 = '11:22:33:44:55:66';
 var ble = chrome.bluetoothLowEnergy;
 
 var errorInProgress = 'In progress';
+var errorNotConnected = 'Not connected';
 
 function expectError(message) {
   if (!chrome.runtime.lastError ||
       chrome.runtime.lastError.message != message)
     chrome.test.sendMessage('Expected error: <' + message + '> got <'
         + chrome.runtime.lastError.message + '>');
 }
 
 function expectSuccess() {
   if (chrome.runtime.lastError)
     chrome.test.sendMessage('Unexpected error: '
         + chrome.runtime.lastError.message);
 }
 
 ble.connect(deviceAddress0, function () {
   expectSuccess();
   ble.disconnect(deviceAddress0, function () {
     chrome.test.succeed();
   });
 
   ble.disconnect(deviceAddress0, function () {
-    expectError(errorInProgress);
-    chrome.test.sendMessage('ready');
+    expectError(errorNotConnected);
+    chrome.test.sendMessage(
+        'After 2nd call to disconnect.');
   });
 });
 
 ble.connect(deviceAddress0, function () {
   expectError(errorInProgress);
-  chrome.test.sendMessage('ready');
+  chrome.test.sendMessage(
+      'After 2nd connect fails due to 1st connect being in progress.');
 });