The console.log exposed to workers just sends the messages to the UI thread for logging...
I forget whether the workaround was done for Firefox or Chrome...I remember hitting it in one or the other, and putting in the workaround for both.
On a related note, transferable objects are handled a bit differently between IE, FF, and Chrome. Some are a bit stricter than others.
We ended up writing a goofy little console.log() replacement that sent messages back to the main UI thread for processing and logging, but that kind of thunking is a might-bit janky.