code: function _areBatchRequirementsMet(batch_ops, completed_ops) {
    var dependencies = common.flatMap(batch_ops, function(op) {
      return OP_DEPENDENCIES[op] || [];
    });
    for (var i = 0; i < dependencies.length; i++) {
      var required_dep = dependencies[i];
      if (batch_ops.indexOf(required_dep) === -1 &&
          completed_ops.indexOf(required_dep) === -1) {
        return false;
      }
    }
    return true;
  }
docs: Tests whether a batch can be started.
  @private
  @param {number[]} batch_ops The operations in the batch we are checking.
  @param {number[]} completed_ops Previously completed operations.
  @return {boolean}