cros: SAML flow use auth code to bootstrap user session

If an auth code is issued for SAML flow, use it to perform
the /MergeSession call to bootstrap the user session.

Bug: 767143
Change-Id: Id42a37c84db468f155edfde557ad789b86ab2c4b
Reviewed-on: https://chromium-review.googlesource.com/677485
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503539}

chrome/browser/chromeos/login/existing_user_controller.cc

@@ -1602,10 +1602,8 @@ void ExistingUserController::DoCompleteLogin(
     return;
   }
 
-  // Fetch OAuth2 tokens if we have an auth code and are not using SAML.
-  // SAML uses cookies to get tokens.
-  if (user_context.GetAuthFlow() == UserContext::AUTH_FLOW_GAIA_WITHOUT_SAML &&
-      !user_context.GetAuthCode().empty()) {
+  // Fetch OAuth2 tokens if we have an auth code.
+  if (!user_context.GetAuthCode().empty()) {
     oauth2_token_initializer_.reset(new OAuth2TokenInitializer);
     oauth2_token_initializer_->Start(
         user_context, base::Bind(&ExistingUserController::OnOAuth2TokensFetched,

chrome/browser/chromeos/login/session/user_session_manager.cc

@@ -1419,11 +1419,13 @@ void UserSessionManager::InitSessionRestoreStrategy() {
     DCHECK(!has_auth_cookies_);
   }
 
-  if (has_auth_cookies_) {
-    session_restore_strategy_ = OAuth2LoginManager::RESTORE_FROM_COOKIE_JAR;
-  } else if (!user_context_.GetRefreshToken().empty()) {
+  if (!user_context_.GetRefreshToken().empty()) {
     session_restore_strategy_ =
         OAuth2LoginManager::RESTORE_FROM_PASSED_OAUTH2_REFRESH_TOKEN;
+  } else if (has_auth_cookies_) {
+    // TODO(b/63865968): Deprecate RESTORE_FROM_COOKIE_JAR after confirming no
+    //   Gaia cookies will be generated out of SAML flow.
+    session_restore_strategy_ = OAuth2LoginManager::RESTORE_FROM_COOKIE_JAR;
   } else {
     session_restore_strategy_ =
         OAuth2LoginManager::RESTORE_FROM_SAVED_OAUTH2_REFRESH_TOKEN;