function _markStart(name, time) {
        if (activeTests[name]) {
            throw new Error("Recursive tests with the same name are not supported. Timer name: " + name);
        }
        
        activeTests[name] = { startTime: time };
    }
@private
Helper function for markStart()

@param {string} name  Timer name.
@param {number} time  Timer start time.