Fix webworker cpu failure over firefox and safari (#1824)
Fix webworker cpu failure over firefox and safari (#1824)

BUG
tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs-core,tensorflow/tfjs-core,tensorflow/tfjs-core,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs-core,tensorflow/tfjs,tensorflow/tfjs-core,tensorflow/tfjs-core,tensorflow/tfjs