Fix crash when signing in to gaia from an incognito tab

chrome/browser/ui/sync/one_click_signin_helper.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/sync/one_click_signin_helper.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/metrics/histogram.h"
@@ skipping 663 matching lines @@
     int route_id) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
   content::WebContents* web_contents = tab_util::GetWebContentsByID(child_id,
                                                                     route_id);
 
   // TODO(mathp): The appearance of this infobar should be tested using a
   // browser_test.
   OneClickSigninHelper* helper =
       OneClickSigninHelper::FromWebContents(web_contents);
+  if (!helper)
+    return;
+
   int error_message_id = 0;
 
   CanOfferFor can_offer_for =
       (auto_accept != AUTO_ACCEPT_EXPLICIT &&
           helper->auto_accept_ != AUTO_ACCEPT_EXPLICIT) ?
           CAN_OFFER_FOR_INTERSTITAL_ONLY : CAN_OFFER_FOR_ALL;
 
   if (!web_contents || !CanOffer(web_contents, can_offer_for, email,
                                  &error_message_id)) {
     VLOG(1) << "OneClickSigninHelper::ShowInfoBarUIThread: not offering";
     if (helper && helper->error_message_.empty() && error_message_id != 0)
       helper->error_message_ = l10n_util::GetStringUTF8(error_message_id);
 
     return;
   }
 
   // Save the email in the one-click signin manager.  The manager may
   // not exist if the contents is incognito or if the profile is already
   // connected to a Google account.
-  if (helper) {
-    if (!session_index.empty())
-      helper->session_index_ = session_index;
+  if (!session_index.empty())
+    helper->session_index_ = session_index;
 
-    if (!email.empty())
-      helper->email_ = email;
+  if (!email.empty())
+    helper->email_ = email;
 
-    if (auto_accept != NO_AUTO_ACCEPT) {
-      helper->auto_accept_ = auto_accept;
-      helper->source_ = source;
-    }
+  if (auto_accept != NO_AUTO_ACCEPT) {
+    helper->auto_accept_ = auto_accept;
+    helper->source_ = source;
   }
 }
 
 void OneClickSigninHelper::RedirectToNTP() {
   // Redirect to NTP with sign in bubble visible.
   content::WebContents* contents = web_contents();
   Profile* profile =
       Profile::FromBrowserContext(contents->GetBrowserContext());
   PrefService* pref_service = profile->GetPrefs();
   pref_service->SetBoolean(prefs::kSyncPromoShowNTPBubble, true);
@@ skipping 113 matching lines @@
         break;
     }
   }
 
   RedirectToNTP();
 }
 
 void OneClickSigninHelper::SigninSuccess() {
   RedirectToNTP();
 }