Background:

For 5.7 binary logs (after WL#7592), the slave applier thread sets
GTID_NEXT according to the Gtid_log_event or Anonymous_log_event
preceding every transaction.  For 5.6 binary logs using GTID_MODE=ON,
it does the same.  But for 5.6 binary log using GTID_MODE=OFF, or for
5.5 or earlier binary logs, there are no Gtid_log_events or
Anonymous_gtid_log_event.  In order to set gtid_next correctly also
for this case, we use a special mechanism: when any
Format_description_log_event is applied, it sets
thd->variables.gtid_next.type=NOT_YET_DETERMINED_GROUP.  The next
statement to execute then sets the real value for gtid_next: if the
next statement is SET GTID_NEXT, then gtid_next is set accordingly. If
the next statement is anything else, it assumes that this is an old
binary log and changes NOT_YET_DETERMINED_GROUP to ANONYMOUS_GROUP.

The code that changes NOT_YET_DETERMINED_GROUP to ANONYMOUS_GROUP
invoked for SQL statements (from mysql_parse). This normally covers
also the RBR case, because RBR transactions begin with a
query_log_event(BEGIN), so it will set gtid_next=ANONYMOUS for the
BEGIN statement.

However, if the applier thread begins execution in the middle of a
transaction, it is possible that a row event is processed when
gtid_next.type is NOT_YET_DETERMINED_GROUP.  This can happen if
an explicit CHANGE MASTER TO RELAY_LOG_POS statement positions the
applier thread after the BEGIN statement, or if an explicit CHANGE
MASTER TO MASTER_LOG_POS statement positions the receiver thread in
the middle of a transaction.  Therefore, even Rows_log_events need to upgrade
NOT_YET_DETERMINED_GROUP to ANONYMOUS.

Problem:

Rows_log_events did not upgrade NOT_YET_DETERMINED to ANONYMOUS.  This
was a regression introduced by WL#7592 step 14.  Prior to WL#7592 step
14, this logic was invoked from the function
gtid_pre_statement_checks, which was invoked from Rows_log_event.
However in WL#7592 step 14, gtid_pre_statement_checks was split into
two functions, gtid_pre_statement_checks and
gtid_pre_statement_post_implicit_commit_checks, where the latter
contained the logic to upgrade NOT_YET_DETERMINED to ANONYMOUS.  The
place where Rows_log_event calls gtid_pre_statement_checks was not
updated so it still only called gtid_pre_statement_checks.

Fix:

Call gtid_pre_statement_post_implicit_commit_checks from
Rows_log_event.