Provide mutable members of UrlRequestContext via pure-virtual interface

chrome/browser/net/chrome_http_user_agent_settings.h

Index: chrome/browser/net/chrome_http_user_agent_settings.h
diff --git a/chrome/browser/net/chrome_http_user_agent_settings.h b/chrome/browser/net/chrome_http_user_agent_settings.h
new file mode 100644
index 0000000000000000000000000000000000000000..a7d390f72fe0ee15b6a5b1c7b6411a2b35f9aad8
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+++ b/chrome/browser/net/chrome_http_user_agent_settings.h
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+// Copyright (c) 2012 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_CHROME_HTTP_USER_AGENT_SETTINGS_H_
+#define CHROME_BROWSER_NET_CHROME_HTTP_USER_AGENT_SETTINGS_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "chrome/browser/api/prefs/pref_member.h"
+#include "net/url_request/http_user_agent_settings.h"
+
+class PrefService;
+
+// An implementation of |HttpUserAgentSettings| that provides HTTP headers
+// Accept-Language and Accept-Charset values that track Pref settings and uses
+// |content::GetUserAgent| to provide the HTTP User-Agent header value.
+class ChromeHttpUserAgentSettings : public net::HttpUserAgentSettings {
+ public:
+  // Must be called on the UI thread.
+  explicit ChromeHttpUserAgentSettings(PrefService* prefs);
+  // Must be called on the IO thread.
+  virtual ~ChromeHttpUserAgentSettings();
+
+  void CleanupOnUIThread();
+
+  // net::HttpUserAgentSettings implementation
+  virtual std::string GetAcceptLanguage() const OVERRIDE;
+  virtual std::string GetAcceptCharset() const OVERRIDE;
+  virtual std::string GetUserAgent(const GURL& url) const OVERRIDE;
+
+ private:
+  StringPrefMember pref_accept_language_;
+  StringPrefMember pref_accept_charset_;
+
+  // Avoid re-processing by caching the last value from the preferences and the
+  // last result of processing via net::HttpUtil::GenerateAccept*Header().
+  mutable std::string last_pref_accept_language_;
+  mutable std::string last_http_accept_language_;
+  mutable std::string last_pref_accept_charset_;
+  mutable std::string last_http_accept_charset_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeHttpUserAgentSettings);
+};
+
+#endif  // CHROME_BROWSER_NET_CHROME_HTTP_USER_AGENT_SETTINGS_H_
+