Client Hints

chrome/browser/net/client_hints.h

Index: chrome/browser/net/client_hints.h
diff --git a/chrome/browser/net/client_hints.h b/chrome/browser/net/client_hints.h
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+// 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/basictypes.h"
+#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/draft2/draft-grigorik-http-client-hints-01.txt
+class ClientHints {
+ public:
+  static const char kDevicePixelRatioHeader[];
+
+  ClientHints();
+  ~ClientHints();
+
+  void Init();
+
+  // Returns the device pixel ratio as a string.  Its value is the same as
+  // window.devicePixelRatio in Javascript.
+  const std::string& GetDevicePixelRatioHeader() const;
+
+ private:
+  friend class ClientHintsTest;
+
+  // Retrieves and updates screen information for use on the IO thread.
+  bool RetrieveScreenInfo();
+
+  void UpdateScreenInfo(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_