Ignore IdToken child result if USM accounts are supported.

The "usm" service flag is not sent in IdToken. After USM support is
launched, we'll want to delete this setting entirely.

Bug: 836246
Change-Id: I4981132619ff1bd580bd10a6a47d7aa088394825
Reviewed-on: https://chromium-review.googlesource.com/1059457Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Commit-Queue: Bruno Kim Medeiros Cesar <brunokim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559053}

chrome/browser/chromeos/login/signin/oauth2_token_initializer.cc

@@ -5,6 +5,7 @@
 #include "chrome/browser/chromeos/login/signin/oauth2_token_initializer.h"
 
 #include "chrome/browser/browser_process.h"
+#include "chrome/common/chrome_features.h"
 
 namespace chromeos {
 
@@ -31,11 +32,14 @@ void OAuth2TokenInitializer::OnOAuth2TokensAvailable(
   user_context_.SetAuthCode(std::string());
   user_context_.SetRefreshToken(result.refresh_token);
   user_context_.SetAccessToken(result.access_token);
+
+  const bool support_usm =
+      base::FeatureList::IsEnabled(features::kCrOSEnableUSMUserService);
   if (result.is_child_account &&
       user_context_.GetUserType() != user_manager::USER_TYPE_CHILD) {
     LOG(FATAL) << "Incorrect child user type " << user_context_.GetUserType();
   } else if (user_context_.GetUserType() == user_manager::USER_TYPE_CHILD &&
-             !result.is_child_account) {
+             !result.is_child_account && !support_usm) {
     LOG(FATAL) << "Incorrect non-child token for the child user.";
   }
   callback_.Run(true, user_context_);