I think the logistics on this would be difficult to implement.
Basically, the plugin would function as a GoldCoin client on the host computer, perhaps as a java applet. As it turns out the back end of the Android App could be used as the underlying platform to handle much of the work of connecting to the GoldCoin network. There may be other java miners out there for coins like Litecoin, which could be ported over.
The next hurdle is the transaction fee. The host will be mining with a CPU, because java runs on the CPU, just like any other app that runs in a browser. The GoldCoin yield with such an app will be very low. This app would have to connect to a pool, to make mining worth while. Solo mining could take months or years to get a block. Because of the low yield from mining, payouts will be expensive. Any amount transmitted below 0.01 will have a 0.1 charge on it. To minimize fees, we would need to have a minimum requirement on mining, such as 1 GLD before it can be paid out.
These are some things that need to be considered by one who wants to program this.