1// Copyright 2013 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef CHROME_BROWSER_NET_CLIENT_HINTS_H_
6#define CHROME_BROWSER_NET_CLIENT_HINTS_H_
7
8#include <string>
9
10#include "base/basictypes.h"
11#include "base/memory/weak_ptr.h"
12
13// ClientHints is a repository in Chrome for information used
14// to create the Client-Hints request header. For more information, see:
15// https://github.com/igrigorik/http-client-hints/blob/draft2/draft-grigorik-http-client-hints-01.txt
16class ClientHints {
17 public:
18  static const char kDevicePixelRatioHeader[];
19
20  ClientHints();
21  ~ClientHints();
22
23  void Init();
24
25  // Returns the device pixel ratio as a string.  Its value is the same as
26  // window.devicePixelRatio in Javascript.
27  const std::string& GetDevicePixelRatioHeader() const;
28
29 private:
30  friend class ClientHintsTest;
31
32  // Retrieves and updates screen information for use on the IO thread.
33  bool RetrieveScreenInfo();
34
35  void UpdateScreenInfo(float device_pixel_ratio_value);
36
37  std::string screen_hints_;
38
39  base::WeakPtrFactory<ClientHints> weak_ptr_factory_;
40
41  DISALLOW_COPY_AND_ASSIGN(ClientHints);
42};
43
44#endif  // CHROME_BROWSER_NET_CLIENT_HINTS_H_
45