Provide mutable members of UrlRequestContext via pure-virtual interface

net/url_request/const_http_user_agent_settings.h

Index: net/url_request/const_http_user_agent_settings.h
diff --git a/net/url_request/const_http_user_agent_settings.h b/net/url_request/const_http_user_agent_settings.h
new file mode 100644
index 0000000000000000000000000000000000000000..b56c03fe3878f454d08a660d58165cd070ce2c3f
--- /dev/null
+++ b/net/url_request/const_http_user_agent_settings.h
@@ -0,0 +1,35 @@
+// 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 NET_URL_REQUEST_CONST_HTTP_USER_AGENT_SETTINGS_H_
+#define NET_URL_REQUEST_CONST_HTTP_USER_AGENT_SETTINGS_H_
+
+#include "net/url_request/const_http_accept_language_and_charset.h"
+
+namespace net {
+
+// An implementation of |HttpUserAgentSettings| that always provides the

[willchan no longer on Chromium, 2012/10/06 19:32:49]

Please name this StaticHttpUserAgentSettings or HttpUserAgentSettingsFixed, as
that's more consistent with existing classes like
StaticSocketDataProvider/StaticCookiePolicy/FixedNonceGenerator/ProxyConfigServiceFixed/etc.

+// same constant values for the HTTP Accept-Language, Accept-Charset, and
+// User-Agent headers.
+class NET_EXPORT ConstHttpUserAgentSettings
+    : public ConstHttpAcceptLanguageAndCharset {

[willchan no longer on Chromium, 2012/10/06 19:32:49]

I don't like implementation inheritance (and the style guide discourages it). Do
you mind using composition instead?

Actually, I looked at this and I think the code sharing is so minimal that I'd
rather just duplicate it and eliminate this extra
ConstHttpAcceptLanguageAndCharset helper class. Its only gain was eliminating
boilerplate when using implementation inheritance, but if we were to use
composition (I hate implementation inheritance enough to be willing to put up
with this minor boilerplate), then the win is too minor to be worth it.

+ public:
+  ConstHttpUserAgentSettings(const std::string& accept_language,
+                             const std::string& accept_charset,
+                             const std::string& user_agent);
+  virtual ~ConstHttpUserAgentSettings() {}
+
+  // ConstHttpAcceptLanguageAndCharset implementation
+  virtual std::string GetUserAgent(const GURL& url) OVERRIDE;
+
+ private:
+  const std::string user_agent_;
+
+  DISALLOW_COPY_AND_ASSIGN(ConstHttpUserAgentSettings);
+};
+
+}  // namespace net
+
+#endif  // NET_URL_REQUEST_CONST_HTTP_USER_AGENT_SETTINGS_H_
+