Object representing a break point. NOTE: This object does not have a reference to the function having break point as this would cause function not to be garbage collected when it is not used any more. We do not want break points to keep functions alive.
function BreakPoint(source_position, opt_script_break_point) {
  this.source_position_ = source_position;
  if (opt_script_break_point) {
    this.script_break_point_ = opt_script_break_point;
  } else {
    this.number_ = next_break_point_number++;
  }
  this.active_ = true;
  this.condition_ = null;
}