Make proxy settings one atomic dictionary in the PrefStores such that modifications are atomic.

chrome/browser/prefs/proxy_config_dictionary.h

Index: chrome/browser/prefs/proxy_config_dictionary.h
diff --git a/chrome/browser/prefs/proxy_config_dictionary.h b/chrome/browser/prefs/proxy_config_dictionary.h
new file mode 100644
index 0000000000000000000000000000000000000000..ae5c80e0b761344b9bfec2462d3b08fcbcaade22
--- /dev/null
+++ b/chrome/browser/prefs/proxy_config_dictionary.h
@@ -0,0 +1,54 @@
+// Copyright (c) 2011 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_PREFS_PROXY_CONFIG_DICTIONARY_H_
+#define CHROME_BROWSER_PREFS_PROXY_CONFIG_DICTIONARY_H_
+#pragma once
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/scoped_ptr.h"
+#include "chrome/browser/prefs/proxy_prefs.h"
+
+class DictionaryValue;
+
+// Factory and wrapper for proxy config dictionaries that are stored
+// in the user preferences. The dictionary has the following structure:
+// {
+//   mode: string,
+//   server: string,
+//   pac_url: string,
+//   bypass_list: string
+// }
+// See proxy_config_dictionary.cc for the structure of the respective strings.
+class ProxyConfigDictionary {
+ public:
+  // Creates a deep copy of |dict| and leaves ownership to caller.
+  explicit ProxyConfigDictionary(const DictionaryValue* dict);
+
+  bool GetMode(ProxyPrefs::ProxyMode* out) const;
+  bool GetPacUrl(std::string* out) const;
+  bool GetProxyServer(std::string* out) const;
+  bool GetBypassList(std::string* out) const;
+
+  static DictionaryValue* CreateDirect();
+  static DictionaryValue* CreateAutoDetect();
+  static DictionaryValue* CreatePacScript(const std::string& pac_url);
+  static DictionaryValue* CreateFixedServers(
+      const std::string& proxy_server,
+      const std::string& bypass_list);
+  static DictionaryValue* CreateSystem();
+ private:
+  static DictionaryValue* CreateDictionary(ProxyPrefs::ProxyMode mode,
+                                           const std::string& pac_url,
+                                           const std::string& proxy_server,
+                                           const std::string& bypass_list);
+
+  scoped_ptr<DictionaryValue> dict_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProxyConfigDictionary);
+};
+
+#endif  // CHROME_BROWSER_PREFS_PROXY_CONFIG_DICTIONARY_H_