Migrate chrome.bluetooth API backend to use device::BluetoothDiscoverySession.

chrome/test/data/extensions/api_test/bluetooth/discovery_in_progress/runtest.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.
 
-var kExpectedDeviceNames = ["d1", "d2"];
+var kExpectedDeviceNames = ["d2"];
 
 function testDiscovery() {
   chrome.test.assertEq(kExpectedDeviceNames.length,
       discoveredDevices.length);
   for (var i = 0; i < kExpectedDeviceNames.length; ++i) {
     chrome.test.assertEq(kExpectedDeviceNames[i],
         discoveredDevices[i].name);
   }
 
   chrome.test.succeed();
@@ skipping 13 matching lines @@
 }
 
 var discoveredDevices = [];
 function recordDevice(device) {
   discoveredDevices.push(device);
 }
 
 chrome.bluetooth.startDiscovery(
     { deviceCallback:recordDevice },
     function() { sendReady(stopDiscoveryAndContinue); });