One of Mozilla’s software developers shared an intriguing image on Google+ recently, and it could be big news for Android users.The image shows a Nexus 4 beaming a Firefox tab to a TV across the room. After the image appeared online, Mozilla was forced to address it, saying that yes, it is working on “second screen support” for a number of devices. This could be Mozilla’s answer to the Google Chromecast.This system appears to be an all software solution, unlike the the Chomecast which requires the $35 HDMI dongle. The Firefox magic is happening with the aid of a Roku box, which is more of an investment than a Chromecast, but already fairly common.The other notable difference here is that the Firefox “experiment” is doing full tab mirroring from a smartphone. The Chomecast can currently only to tab casting from a desktop PC over local WiFi. Mozilla could be leveraging some sort of WebRTC layer, support for which was just added to the mobile app a few weeks ago. It may or may not require an internet connection — Mozilla isn’t saying.The Google Chromecast was a huge seller when it launched at the end of July. It sold out on Amazon in mere hours, and Google’s own Play Store was backordered for weeks. Mozilla isn’t really in the hardware business, so it makes sense to roll a similar feature out using third-party devices like the Roku.Mozilla refused to speculate about when users would get to try out its tab mirroring feature.