On a L2 network, when a client roams from an AP1 to AP2 the mac address tables of the switches on the L2 LAN are automatically updated.
When the client roams and establish a new connected with AP2 then AP2 sends LLC frames on the LAN as broadcast with the MAC address of the client as source address. All the switches on the L2 LAN receive this packet and update their MAC address table consequently.
If AP and client are configured with the option ""Client Bridge Support"", the client may have several MAC address on its LAN side, these MAC addresses aren't masqueraded. When it roams the AP wsend 3 LLC frames on the LAN for each MAC address behind the client.
See attached a screenshot of the LLC frames sent by the AP on the LAN.