Move system.* family of APIs to extensions/

chrome/browser/extensions/api/system_info/system_info_provider.h

-// 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.
-
-#ifndef CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_SYSTEM_INFO_PROVIDER_H_
-#define CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_SYSTEM_INFO_PROVIDER_H_
-
-#include <queue>
-
-#include "base/bind.h"
-#include "base/callback.h"
-#include "base/memory/ref_counted.h"
-#include "base/threading/sequenced_worker_pool.h"
-
-namespace extensions {
-
-// An abstract base class for all kinds of system information providers. Each
-// kind of SystemInfoProvider is a single shared instance. It is created if
-// needed, and destroyed at exit time. This is done via LazyInstance and
-// scoped_refptr.
-//
-// The SystemInfoProvider is designed to query system information on the worker
-// pool. It also maintains a queue of callbacks on the UI thread which are
-// waiting for the completion of querying operation. Once the query operation
-// is completed, all pending callbacks in the queue get called on the UI
-// thread. In this way, it avoids frequent querying operation in case of lots
-// of query requests, e.g. calling systemInfo.cpu.get repeatedly in an
-// extension process.
-//
-// Each kind of SystemInfoProvider should satisfy an API query in a subclass on
-// the blocking pool.
-class SystemInfoProvider
-    : public base::RefCountedThreadSafe<SystemInfoProvider> {
- public:
-  // Callback type for completing to get information. The argument indicates
-  // whether its contents are valid, for example, no error occurs in querying
-  // the information.
-  typedef base::Callback<void(bool)> QueryInfoCompletionCallback;
-  typedef std::queue<QueryInfoCompletionCallback> CallbackQueue;
-
-  SystemInfoProvider();
-
-  // Override to do any prepare work on UI thread before |QueryInfo()| gets
-  // called.
-  virtual void PrepareQueryOnUIThread();
-
-  // The parameter |do_query_info_callback| is query info task which is posted
-  // to SystemInfoProvider sequenced worker pool.
-  //
-  // You can do any initial things of *InfoProvider before start to query info.
-  // While overriding this method, |do_query_info_callback| *must* be called
-  // directly or indirectly.
-  //
-  // Sample usage please refer to StorageInfoProvider.
-  virtual void InitializeProvider(const base::Closure& do_query_info_callback);
-
-  // Start to query the system information. Should be called on UI thread.
-  // The |callback| will get called once the query is completed.
-  //
-  // If the parameter |callback| itself calls StartQueryInfo(callback2),
-  // callback2 will be called immediately rather than triggering another call to
-  // the system.
-  void StartQueryInfo(const QueryInfoCompletionCallback& callback);
-
- protected:
-  virtual ~SystemInfoProvider();
-
- private:
-  friend class base::RefCountedThreadSafe<SystemInfoProvider>;
-
-  // Interface to query the system information synchronously.
-  // Return true if no error occurs.
-  // Should be called in the blocking pool.
-  virtual bool QueryInfo() = 0;
-
-  // Called on UI thread. The |success| parameter means whether it succeeds
-  // to get the information.
-  void OnQueryCompleted(bool success);
-
-  void StartQueryInfoPostInitialization();
-
-  // The queue of callbacks waiting for the info querying completion. It is
-  // maintained on the UI thread.
-  CallbackQueue callbacks_;
-
-  // Indicates if it is waiting for the querying completion.
-  bool is_waiting_for_completion_;
-
-  // Sequenced worker pool to make the operation of querying information get
-  // executed in order.
-  scoped_refptr<base::SequencedTaskRunner> worker_pool_;
-
-  DISALLOW_COPY_AND_ASSIGN(SystemInfoProvider);
-};
-
-}  // namespace extensions
-
-#endif  // CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_SYSTEM_INFO_PROVIDER_H_