Add the implementation skeleton for systeminfo.cpu API

chrome/test/data/extensions/api_test/systeminfo/cpu/test_cpuinfo_api.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.
+
+// systeminfo.cpu api test
+// browser_tests.exe --gtest_filter=SysteminfoCpuApiTest.*
+
+chrome.systeminfo = chrome.experimental.systeminfo;
+
+chrome.test.runTests([
+  function testGet() {
+    chrome.systeminfo.cpu.get(chrome.test.callbackPass(function(result){
+      chrome.test.assertTrue(result.cores.length == 1);
+      var core = result.cores[0];
+      chrome.test.assertTrue(core.load == 53);
+    }));
+  },
+]);
+