Try typing the letter 'a' into either field below. The bottom
field allows for multiple selection by comma-delimiting the values. Note that
already-selected values don't show up in the dropdown.
I've manually added a 125ms delay to populating of the dropdown to synthesize a JS remoting call. If you'd like to see it without that delay, replace the setTimeout call a the end of the nameCallback function with the value listed in the comments. Note that there is also a 250ms delay between the last keypress and triggering the dropdown, so typing multiple characters doesn't create unneeded churn. In the stock configuration, you should see the "Loading..." dropdown 250ms after typing a character, and then 125ms later, the dropdown with values should appear.