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
new file mode 100644
index 0000000000000000000000000000000000000000..42e47445dfea97b7149dc49e6bd07d8336a49ca8
--- /dev/null
+++ b/chrome/browser/net/client_hints.h
@@ -0,0 +1,44 @@
+// 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"

[mmenke, 2013/09/25 17:37:40]

nit:  include basictypes.h for DISALLOW_COPY_AND_ASSIGN

[bengr, 2013/09/25 20:04:12]

Done.

+
+// 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();
+
+  // Retrieves screen information for use on the IO thread.
+  bool RetrieveScreenInfo();

[mmenke, 2013/09/25 17:37:40]

Optional:  Suggest "UpdateScreenInfo" to make it clearer that it modifies this,
instead of just retrieves a value.

Also, should this be public?  Ideally, the ClientHints object would watch for
changes itself, or through its own listener on the UI thread.

[bengr, 2013/09/25 20:04:12]

I changed the comment slightly instead. There's already an UpdateScreenInfo(),
so I wanted to avoid having to rename the other one as well.

+
+  // 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.

[mmenke, 2013/09/25 17:37:40]

Comment is also incorrect.

Suggest something along the lines of "Returns the pixel ration as a string.  Its
value is the same as window.devicePixelRatio in Javascript."

[bengr, 2013/09/25 20:04:12]

Done.

+  const std::string& GetDevicePixelRatioHeader() const;
+
+ private:
+  friend class ClientHintsTest;
+
+  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_