ScrollJank with WebPageTest

index.js

// More details in blog post at 
/*****
http://bit.ly/wpt-scrolljank
*****/

var url = 'http://nparashuram.com/perfslides';

var wptUrl = 'http://192.168.254.21'; // Location of WPT instance
var POLLING_INTERVAL = 1000 * 10; // Look every 10 seconds

var request = require('request');

function runTest(url, cb) {
	var formData = {
		url: url,
		where: 'Test_loc',
		browser: 'Chrome',
		location: 'Test:Chrome.Cable',
		runs: 1,
		fvonly: 1,
		video: 'on',
		trace: 'on',
		f: 'json',
		cmdline: '--enable-gpu-benchmarking --enable-thread-composting',
		script: '\nnavigate\t' + url + '\nexecAndWait	window.chrome.gpuBenchmarking.smoothScrollBy(5000,function(){},0.5,0.5,chrome.gpuBenchmarking.DEFAULT_INPUT,"down",500);'
	};

	console.log('Starting test on', url);
	request.post({
		url: wptUrl + '/runtest.php',
		formData: formData
	}, function(err, httpResponse, body) {
		if (err) {
			cb(err);
		} else {
			console.log('Test submitted successfully');
			isTestDone(JSON.parse(body).data.jsonUrl, cb);
		}
	});
}

function isTestDone(url, cb) {
	console.log('Checking status on ', url);
	(function repeat() {
		request.get(url, function(err, resp, body) {
			if (err) {
				console.log('Error in status URL');
				cb(err);
			}
			var data = JSON.parse(body);
			if (data.statusCode !== 200) {
				console.log(data.statusText);
				setTimeout(repeat, POLLING_INTERVAL);
			} else {
				cb(undefined, data);
			}
		});
	})();
}

function getLogs(testId, cb) {
	var fileUrl = wptUrl + '/getgzip.php?file=1_trace.json&test=' + testId;
	console.log('Fetching Logs from ', fileUrl);

	var rasterize_time = [],
		rasterized_pixel_count = [],
		frame_times = [],
		frame_timestamps = [],
		total = 0;

	request(fileUrl, function(err, resp, body) {
		var log = JSON.parse(body);
		var first_frame = true;
		log.traceEvents.forEach(function(event) {
			if (event.name === 'BenchmarkInstrumentation::ImplThreadRenderingStats' || event.name === 'BenchmarkInstrumentation::MainThreadRenderingStats') {
				var frame_count = event.args['data']['frame_count'];
				if (frame_count > 1) throw 'trace contains multi-frame render stats'
				if (frame_count == 1) {
					frame_timestamps.push(event.ts / 1000);
					if (!first_frame) {
						frame_times.push(frame_timestamps[frame_timestamps.length - 1] - frame_timestamps[frame_timestamps.length - 2]);
						total += frame_times[frame_times.length - 1];
					}
					first_frame = false;
				}
				rasterize_time.push(1000.0 * event.args['data']['rasterize_time']);
				rasterized_pixel_count.push(event.args['data']['rasterized_pixel_count']);
			}
		});

		cb(total / frame_times.length);
	});
}

runTest(url, function(err, data) {
	var id = data.data.id;
	getLogs(id, console.log.bind(console));
});

//getLogs('141219_A4_F', console.log.bind(console));