The chart above shows that Firefox has been able to overtake Chrome over the past two months. Tests are conducted daily. Performance is measured through execution time (in ms), so the lower the points on the graph, the faster the performance.
It was released for the first time 2007 by WebKit, and is a legacy reference standard at the moment, last updated in 2013. Since then it has been superseded for about a decade by newer benchmarks like Google's V8 and Octane. That's why the victory, although commendable, may not be particularly important.