anchor.diff:        try {
           token = TokenInfo.fromJson(json.decode(tokenJson) as Map<String, dynamic>);
         } on FormatException {
  +        log.warning('Failed to decode token JSON: $tokenJson');
           throw InternalServerError('Invalid JSON: "$tokenJson"');
         }
   
  
positive.code:     // Authenticate as a signed-in Google account via OAuth id token.
      final HttpClient client = httpClientProvider();
      try {
        final HttpClientRequest verifyTokenRequest = await client.getUrl(Uri.https(
          'oauth2.googleapis.com',
          '/tokeninfo',
  
negative.code: 
        return AuthenticatedContext(agent: agent, clientContext: clientContext);
      } else if (swarmingToken != null) {
        log.debug('Authenticating as swarming task');
        return await authenticateAccessToken(swarmingToken, clientContext: clientContext, log: log);
      }
  
  