Make sure to display an errors that occur during the chrome sign in process

chrome/browser/ui/webui/sync_promo/sync_promo_handler.cc

 // 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.
 
 #include "chrome/browser/ui/webui/sync_promo/sync_promo_handler.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/metrics/histogram.h"
 #include "base/time.h"
@@ skipping 62 matching lines @@
 
 SyncPromoHandler::~SyncPromoHandler() {
 }
 
 // static
 void SyncPromoHandler::RegisterUserPrefs(PrefService* prefs) {
   prefs->RegisterIntegerPref(prefs::kSyncPromoViewCount, 0,
       PrefService::UNSYNCABLE_PREF);
   prefs->RegisterBooleanPref(prefs::kSyncPromoShowNTPBubble, false,
       PrefService::UNSYNCABLE_PREF);
+  prefs->RegisterStringPref(prefs::kSyncPromoErrorMessage, std::string(),
+      PrefService::UNSYNCABLE_PREF);
 }
 
 void SyncPromoHandler::RegisterMessages() {
   // Keep a reference to the preferences service for convenience and it's
   // probably a little faster that getting it via Profile::FromWebUI() every
   // time we need to interact with preferences.
   prefs_ = Profile::FromWebUI(web_ui())->GetPrefs();
   DCHECK(prefs_);
   // Ignore events from view-source:chrome://signin.
   if (!web_ui()->GetWebContents()->GetController().GetActiveEntry()->
@@ skipping 187 matching lines @@
   // Send an enumeration to our single user flow histogram.
   UMA_HISTOGRAM_ENUMERATION("SyncPromo.UserFlow", action,
                             SYNC_PROMO_BUCKET_BOUNDARY);
 }
 
 void SyncPromoHandler::CloseUI() {
   // Callers should not ever try to close the promo UI (should only call
   // CloseUI() if the user is already logged in).
   NOTREACHED() << "Cannot close the promo UI";
 }