Add support for sending a USB SET_CONFIGURATION request.

extensions/test/data/api_test/usb/set_configuration/test.js

+// Copyright (c) 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 usb = chrome.usb;
+
+var tests = [
+  function setConfiguration() {
+    usb.findDevices({vendorId: 0, productId: 0}, function (devices) {
+      var device = devices[0];
+      usb.getConfiguration(device, function (result) {
+        chrome.test.assertLastError("The device is not in a configured state.");
+        usb.setConfiguration(device, 1, function (result) {
+          chrome.test.assertNoLastError();
+          chrome.test.assertTrue(result);
+          usb.getConfiguration(device, function (result) {
+            chrome.test.assertNoLastError();
+            chrome.test.succeed();
+          });
+        });
+      });
+    });
+  }
+];
+
+chrome.test.runTests(tests);