This function is implemented by FrameXML in FrameXML/ChatFrame.lua.

ChatFrame_AddChannel(chatFrame, 'channelName');

Order a chat frame to display a previously-joined chat channel

Parameters

Arguments

(chatFrame, 'channelName')

chatFrame 

Object - The chat frame to display the channel in. Some ex

channelName 

String - The name of the chatchannel to activate.

Returns

nil

Example

ChatFrame_AddChannel(DEFAULT_CHAT_FRAME, "test");
ChatFrame_AddChannel(SELECTED_CHAT_FRAME, "ErrorInfo");
ChatFrame_AddChannel(ChatFrame1, "AnotherChannel");

chatFrame

DEFAULT_CHAT_FRAME - Adds the channel to the default chat window.
SELECTED_CHAT_FRAME - Adds the channel in the chat window with focus ( the front window ).
ChatFrameX - Where X is an int from 1 to 10. Seems to add the channel to any chat window, where X=1 is the left-most window.