Refine systemInfo.cpu API defintions and provide systemInfo.cpu.get impl for Windows and Linux

base/sys_info_mac.cc

 // 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.
 
 #include "base/sys_info.h"
 
 #include <ApplicationServices/ApplicationServices.h>
 #include <CoreServices/CoreServices.h>
 #include <mach/mach_host.h>
 #include <mach/mach_init.h>
@@ skipping 36 matching lines @@
                          reinterpret_cast<host_info_t>(&hostinfo),
                          &count);
   if (result != KERN_SUCCESS) {
     NOTREACHED();
     return 0;
   }
   DCHECK_EQ(HOST_BASIC_INFO_COUNT, count);
   return static_cast<int64>(hostinfo.max_mem);
 }
 
+// static
+std::string SysInfo::CPUModelName() {
+  // TODO(hongbo): Retrive cpu model name.
+  return "unknown";
+}
+
 }  // namespace base