Updated Client-Hints patch

chrome/browser/net/client_hints.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_NET_CLIENT_HINTS_H_
+#define CHROME_BROWSER_NET_CLIENT_HINTS_H_
+
+#include <string>
+
+#include "base/memory/weak_ptr.h"
+
+// ClientHints is a repository in Chrome for information used
+// to create the Client-Hints request header. For more information, see:
+// https://github.com/igrigorik/http-client-hints/blob/master/draft-grigorik-http-client-hints-01.txt
+class ClientHints {
+ public:
+  ClientHints();
+  ~ClientHints();
+
+  void Init();
+
+  // Retrieves screen information for use on the IO thread.
+  bool RetrieveScreenInfo();
+
+  // Returns client hints pertaining to screen information. The format is:
+  // "dpr=x", where x is pixel ratio. Its value is the same as the value
+  // returned by the JavaScript command window.devicePixelRatio
+  const std::string& GetString() const;
+
+ private:
+  friend class ClientHintsTest;
+
+  void UpdateScreenInfo(const float* device_pixel_ratio_value);
+
+  std::string screen_hints_;
+
+  base::WeakPtrFactory<ClientHints> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ClientHints);
+};
+
+#endif  // CHROME_BROWSER_NET_CLIENT_HINTS_H_