After increasing user name length mysql.db is reported broken and event scheduler does not start

--source include/not_embedded.inc

alter table mysql.user modify User char(80) binary not null default '';

alter table mysql.db modify User char(80) binary not null default '';

alter table mysql.tables_priv modify User char(80) binary not null default '';

alter table mysql.columns_priv modify User char(80) binary not null default '';

alter table mysql.procs_priv modify User char(80) binary not null default '';

alter table mysql.proc modify definer char(141) collate utf8_bin not null default '';

alter table mysql.event modify definer char(141) collate utf8_bin not null default '';

flush privileges;

--enable_reconnect

--append_file $MYSQLTEST_VARDIR/tmp/mysqld.1.expect

restart

EOF

--shutdown_server 60

--source include/wait_until_connected_again.inc

set global event_scheduler = on;

select @@event_scheduler;

alter table mysql.user modify User char(16) binary not null default '';

alter table mysql.db modify User char(16) binary not null default '';

alter table mysql.tables_priv modify User char(16) binary not null default '';

alter table mysql.columns_priv modify User char(16) binary not null default '';

alter table mysql.procs_priv modify User char(16) binary not null default '';

alter table mysql.proc modify definer char(77) collate utf8_bin not null default '';

alter table mysql.event modify definer char(77) collate utf8_bin not null default '';

set global event_scheduler = off;

CURRENT_TEST: bug.t1

mysqltest: At line 19: query 'set global event_scheduler = on' failed: 1577: Cannot proceed because system tables used by Event Scheduler were found damaged at server start

130512 17:22:23 [ERROR] Incorrect definition of table mysql.db: expected column 'User' at position 2 to have type char(16), found type char(80).

130512 17:22:23 [ERROR] Event Scheduler: An error occurred when initializing system tables. Disabling the Event Scheduler.

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