CLONE - A student can disable the chat window auto-scroll

1. As admin go to Site administration>Plugins>Activity modules>Chat and set the Chat method to "Normal method"
2. Login as a student and access a chat activity.
3. Click to enter the chat and add a number of chat messages until they begin to scroll automatically.
4. Un-check the auto scroll checkbox beside the text input field.
5. Add more chat messages and check that they no longer scroll automatically.