Fix account_reconcilor crash.

components/signin/core/browser/account_reconcilor.cc

 // Copyright 2014 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 "components/signin/core/browser/account_reconcilor.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/json/json_reader.h"
@@ skipping 643 matching lines @@
       merge_session_helper_.SignalComplete(
           add_to_cookie_copy[i],
           GoogleServiceAuthError::AuthErrorNone());
     } else {
       PerformMergeAction(add_to_cookie_copy[i]);
       added_to_cookie++;
     }
   }
 
   // For each account in the gaia cookie not known to chrome,
-  // PerformAddToChromeAction.
+  // PerformAddToChromeAction. Make a copy of |add_to_chrome| since calls to
+  // PerformAddToChromeAction() may modify this array.
+  std::vector<std::pair<std::string, int> > add_to_chrome_copy = add_to_chrome_;
   for (std::vector<std::pair<std::string, int> >::const_iterator i =
-           add_to_chrome_.begin();
-       i != add_to_chrome_.end();
+           add_to_chrome_copy.begin();
+       i != add_to_chrome_copy.end();
        ++i) {
     PerformAddToChromeAction(i->first, i->second);
   }
 
   signin_metrics::LogSigninAccountReconciliation(valid_chrome_accounts_.size(),
                                                  added_to_cookie,
                                                  add_to_chrome_.size(),
                                                  are_primaries_equal,
                                                  first_execution_);
   first_execution_ = false;
@@ skipping 94 matching lines @@
 
 void AccountReconcilor::HandleRefreshTokenFetched(
     const std::string& account_id,
     const std::string& refresh_token) {
   if (!refresh_token.empty())
     PerformAddAccountToTokenService(account_id, refresh_token);
 
   MarkAccountAsAddedToChrome(account_id);
   CalculateIfReconcileIsDone();
 }