Change getDevices to use a DeviceCallback.

chrome/test/data/extensions/api_test/bluetooth/test_getdevices_concurrently.js

+// Copyright (c) 2012 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.
+
+function testGetDevicesConcurrently() {
+  chrome.test.assertEq(1, errors.length);
+
+  var kExpectedError = "Concurrent calls to getDevices are not allowed.";
+  chrome.test.assertEq(kExpectedError, errors[0]);
+
+  chrome.test.succeed();
+}
+
+function nop() {}
+
+var errors = [];
+function recordError() {
+  if (chrome.runtime.lastError) {
+    errors.push(chrome.runtime.lastError.message);
+  }
+}
+
+var getDevicesOptions = { deviceCallback:nop, name:'foo' };
+chrome.experimental.bluetooth.getDevices(getDevicesOptions, recordError);
+chrome.experimental.bluetooth.getDevices(getDevicesOptions, recordError);
+chrome.test.sendMessage('ready',
+    function(message) {
+      chrome.test.runTests([
+          testGetDevicesConcurrently
+      ]);
+  });