Remove unused Logger#_mkRecord

lib/bunyan.js

@@ -702,21 +702,6 @@ Logger.prototype._applySerializers = function (fields, excludeFields) {
 }
 
 
-/**
- * A log record is a 4-tuple:
- *    [<default fields object>,
- *     <log record fields object>,
- *     <level integer>,
- *     <msg args array>]
- * For Perf reasons, we only render this down to a single object when
- * it is emitted.
- */
-Logger.prototype._mkRecord = function (fields, level, msgArgs) {
-    var recFields = (fields ? objCopy(fields) : null);
-    return [this.fields, recFields, level, msgArgs];
-}
-
-
 /**
  * Emit a log record.
  *