In my recent project, I tried to using actionscript worker with flex sdk 4.5.
1. download and unpack AIR SDK 3.5 to the root directory of Flex SDK 4.5
2. create a project using flash builder and add some simple code from WorkerFactory
When I tried to run the simple project, I got an error from flash builder:
Class flash.system::MessageChannel could not be found
After googled a lot, I got some idea from here
To solve this problem, just add compiler arguments as below: