支持HTML5的浏览器都可以运行（IE9+FF+Chrome）
Total总时长
performance.timing.loadEventEnd - performance.timing.navigationStart
DNS查询时间
performance.timing.domainLookupEnd - performance.timing.domainLookupStart
服务器处理时间
performance.timing.responseStart - performance.timing.requestStart
客户白屏时间
performance.timing.domInteractive - performance.timing.navigationStart
详细时间轴
更多资料参考
http://dvcs.w3.org/hg/webperf/raw-file/tip/specs/NavigationTiming/Overview.html