Move the USB API tests into app_shell_browsertests.

chrome/test/data/extensions/api_test/usb/zero_length_transfer/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.usb;
-
-var tests = [
-  function zeroLengthTransfer() {
-    usb.findDevices({vendorId: 0, productId: 0}, function(devices) {
-      var device = devices[0];
-      var transfer = new Object();
-      transfer.direction = "out";
-      transfer.endpoint = 1;
-      transfer.data = new ArrayBuffer(0);
-      usb.bulkTransfer(device, transfer, function (result) {
-        chrome.test.succeed();
-      });
-    });
-  },
-];
-
-chrome.test.runTests(tests);