Add a missing const qualifier

storage/innobase/data/data0data.cc

@@ -803,14 +803,11 @@ big_rec_t::alloc(
 	return(rec);
 }
 
-/** Create a deep copy of this object
-@param[in]	heap	the memory heap in which the clone will be
-			created.
-
-@return	the cloned object. */
+/** Create a deep copy of this object.
+@param[in,out]	heap	memory heap in which the clone will be created
+@return	the cloned object */
 dfield_t*
-dfield_t::clone(
-	mem_heap_t*	heap)
+dfield_t::clone(mem_heap_t* heap) const
 {
 	const ulint size = len == UNIV_SQL_NULL ? 0 : len;
 	dfield_t* obj = static_cast<dfield_t*>(

storage/innobase/include/data0data.h

 /*****************************************************************************
 
 Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -586,11 +587,10 @@ struct dfield_t{
 	unsigned	len;	/*!< data length; UNIV_SQL_NULL if SQL null */
 	dtype_t		type;	/*!< type of data */
 
-	/** Create a deep copy of this object
-	@param[in]	heap	the memory heap in which the clone will be
-				created.
-	@return	the cloned object. */
-	dfield_t* clone(mem_heap_t* heap);
+	/** Create a deep copy of this object.
+	@param[in,out]	heap	memory heap in which the clone will be created
+	@return	the cloned object */
+	dfield_t* clone(mem_heap_t* heap) const;
 };
 
 /** Structure for an SQL data tuple of fields (logical record) */