Building a more power-efficient browser
They can start to compare themselves against Chrome when they are at least at feature parity with HTML5, CSS3, Ecmascript6, work cross-platform (not just on Microsoft-owned platforms), and have useable developer tools. I'm not sure I know of any professional web developers that don't view IE/Edge as an afterthought still. We build our applications in Chrome/FF, using Chrome/FF, and occasionally test to make sure the experiences don't totally suck in the others. They are also missing something like Electron, which is used a lot to build native cross-platform apps using web technologies.Power efficient is nice, but today's mobile phones have much lower hanging fruit -- you could run the CPU for days at 100% if you didn't care about the display/backlight, cellular radio, or GPS. If you don't believe me put your phone in airplane mode and play a video or game on loop with the brightness turned all the way down.