Allow sync with 2-factor StrongAuth accounts in ChromeOS.

chrome/browser/sync/signin_manager.cc

Index: chrome/browser/sync/signin_manager.cc
diff --git a/chrome/browser/sync/signin_manager.cc b/chrome/browser/sync/signin_manager.cc
index b64b3bb461a9efb5a06018ea1a4c2f9a221b088e..1a884970b52c131c7a5bc0e6da47d326bc7e8db5 100644
--- a/chrome/browser/sync/signin_manager.cc
+++ b/chrome/browser/sync/signin_manager.cc
@@ -49,9 +49,12 @@ void SigninManager::StartSignIn(const std::string& username,
                                 const std::string& login_token,
                                 const std::string& login_captcha) {
   DCHECK(username_.empty());
+#if !defined(OS_CHROMEOS)
   // The Sign out should clear the token service credentials.
+  // Note: In CHROMEOS we might have valid credentials but still need to
+  // set up 2-factor authentication.
   DCHECK(!profile_->GetTokenService()->AreCredentialsValid());
-
+#endif
   username_.assign(username);
   password_.assign(password);