Provide mutable members of UrlRequestContext via pure-virtual interface

chrome/browser/net/chrome_http_user_agent_settings.h

+// 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);
+  virtual ~ChromeHttpUserAgentSettings() {}

[willchan no longer on Chromium, 2012/10/24 03:40:10]

Define it in the .cc please. This "empty" destructor will need to inline the
calls to teardown the vtable entries and invoke the parent destructor and also
inline all the std::string destructors for the member variables. Thus, it's
non-trivial and causes code bloat.

[erikwright (departed), 2012/10/24 13:14:33]

I think this should not be inline. It's presumably non-trivial due to non-POD
members.

Is it to be destroyed on IO or UI thread? Please specify in comment and DCHECK.

+
+  void CleanupOnUIThread();
+
+  // net::HttpUserAgentSettings implementation
+  virtual std::string GetAcceptLanguage() OVERRIDE;
+  virtual std::string GetAcceptCharset() OVERRIDE;
+  virtual std::string GetUserAgent(const GURL& url) 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().
+  std::string last_pref_accept_language_;
+  std::string last_http_accept_language_;
+  std::string last_pref_accept_charset_;
+  std::string last_http_accept_charset_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeHttpUserAgentSettings);
+};
+
+#endif  // CHROME_BROWSER_NET_CHROME_HTTP_USER_AGENT_SETTINGS_H_
+