First paint is always 0

[danschultz]

I'm not sure if this is an issue with bigrigrunner or the bigrig cli tool, but when analyzing the test results, the time to first paint is always 0ms. I'm using the latest version at HEAD (d08ffaa)

Repro:

> bigrigrunner -u http://www.google.com/analytics -s ".footer-lower" -t load | bigrig
[{"start":0,"end":2834.352000117302,"duration":2834.352000117302,"parseHTML":8.864999999999919,"javaScript":226.60300000000018,"styles":83.74599999999982,"updateLayerTree":7.65,"layout":67.83800000000002,"paint":6.620000000000001,"raster":60.55400000000002,"composite":0.288000000000153,"extendedInfo":{"domContentLoaded":1258.795000076294,"loadTime":1803.8500000238419,"firstPaint":0,"javaScript":{"www.google.com":10.734000000000052,"www.gstatic.com":21.364999999999988,"ajax.googleapis.com":111.30799999999998,"www.googletagmanager.com":24.01400000000009,"www.google-analytics.com":42.39600000000013,"www.googleapis.com":0.235}},"title":"Load","type":"Load"}]