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

chrome/browser/policy/managed_prefs_banner_base.cc

Index: chrome/browser/policy/managed_prefs_banner_base.cc
diff --git a/chrome/browser/policy/managed_prefs_banner_base.cc b/chrome/browser/policy/managed_prefs_banner_base.cc
index 826f4536766fc3270b7699231084ff6695e2092f..9bdafba6874ae28749c79b637170ad92305c09b6 100644
--- a/chrome/browser/policy/managed_prefs_banner_base.cc
+++ b/chrome/browser/policy/managed_prefs_banner_base.cc
@@ -85,10 +85,7 @@ void ManagedPrefsBannerBase::Init(PrefService* local_state,
 #if defined(GOOGLE_CHROME_BUILD)
       AddLocalStatePref(prefs::kMetricsReportingEnabled);
 #endif
-      AddUserPref(prefs::kProxyMode);
-      AddUserPref(prefs::kProxyServer);
-      AddUserPref(prefs::kProxyPacUrl);
-      AddUserPref(prefs::kProxyBypassList);
+      AddUserPref(prefs::kProxy);
       break;
     default:
       NOTREACHED();