Polish the SystemInfoProvider template code and refactor StorageInfoProvider based on it

chrome/browser/extensions/api/system_info_cpu/cpu_info_provider_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 "chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.h"
 
 namespace extensions {
 
+namespace {
+
 using api::experimental_system_info_cpu::CpuInfo;
 
 // CpuInfoProvider implementation on Mac OS.
 class CpuInfoProviderMac : public CpuInfoProvider {
  public:
   CpuInfoProviderMac() {}
   virtual ~CpuInfoProviderMac() {}
   virtual bool QueryInfo(CpuInfo* info) OVERRIDE;
 };
 
 bool CpuInfoProviderMac::QueryInfo(CpuInfo* info) {
   // TODO(hmin): not implemented yet.
   return false;
 }
 
+}  // namespace
+
 // static
-template<>
 CpuInfoProvider* CpuInfoProvider::Get() {
   return CpuInfoProvider::GetInstance<CpuInfoProviderMac>();
 }
 
 }  // namespace extensions