static all(operations) {
    return new shaka.util.AbortableOperation(
        Promise.all(operations.map((op) => op.promise)),
        () => Promise.all(operations.map((op) => op.abort())));
  }
@param {!Array<!shaka.util.AbortableOperation>} operations
@return {!shaka.util.AbortableOperation} An operation which is resolved
  when all operations are successful and fails when any operation fails.
  For this operation, abort() aborts all given operations.
@export