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 2ab04f89704f96059a3865a67e7bf74fe2f95917..3415f18b28de70fc246fd15d270c1f4a2b6e7b8f 100644
--- a/chrome/browser/prefs/pref_service.cc
+++ b/chrome/browser/prefs/pref_service.cc
@@ -240,10 +240,19 @@ 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(