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

chrome/browser/prefs/pref_service.cc

Index: chrome/browser/prefs/pref_service.cc
diff --git a/chrome/browser/prefs/pref_service.cc b/chrome/browser/prefs/pref_service.cc
index f5a62521afdbc4e0723368e324a91d2626731ecc..56ee2b18721dc7ca85ef89e30b03858fa30818e3 100644
--- a/chrome/browser/prefs/pref_service.cc
+++ b/chrome/browser/prefs/pref_service.cc
@@ -251,10 +251,19 @@ void PrefService::RegisterListPref(const char* path) {
   RegisterPreference(path, new ListValue());
 }
 
+void PrefService::RegisterListPref(const char* path, ListValue* default_value) {
+  RegisterPreference(path, default_value);
+}
+
 void PrefService::RegisterDictionaryPref(const char* path) {
   RegisterPreference(path, new DictionaryValue());
 }
 
+void PrefService::RegisterDictionaryPref(const char* path,
+                                         DictionaryValue* default_value) {
+  RegisterPreference(path, default_value);
+}
+
 void PrefService::RegisterLocalizedBooleanPref(const char* path,
                                                int locale_default_message_id) {
   RegisterPreference(