Move system.* family of APIs to extensions/

extensions/common/api/system_memory.idl

 // Copyright 2013 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.
 
 // The <code>chrome.system.memory</code> API.
 namespace system.memory {
 
   dictionary MemoryInfo {
     // The total amount of physical memory capacity, in bytes.
     double capacity;
     // The amount of available capacity, in bytes.
     double availableCapacity;
   };
 
   callback MemoryInfoCallback = void (MemoryInfo info);
 
   interface Functions {
     // Get physical memory information.
     static void getInfo(MemoryInfoCallback callback);
   };
 };