Adding tests for USB extension API

chrome/test/data/extensions/api_test/usb/device_handling/test.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 usb = chrome.experimental.usb;
+
+var tests = [
+  function implicitCloseDevice() {
+    usb.findDevice(0, 0, {}, function(device) {
+      chrome.test.succeed();
+    });
+  },
+  function explicitCloseDevice() {
+    usb.findDevice(0, 0, {}, function(device) {
+      usb.closeDevice(device);
+      chrome.test.succeed();
+    });
+  },
+];
+
+chrome.test.runTests(tests);