Add test data for spaceport benchmark.

chrome/test/data/third_party/spaceport/js/tests/audioLatency.js

+define([ 'util/ensureCallback', 'util/cacheBust', 'util/timeout' ], function (ensureCallback, cacheBust, timeout) {
+    var MAX_LATENCY = 20;
+
+    function getPlayLatency(audio, callback) {
+        callback = ensureCallback(callback);
+
+        var startTime;
+
+        function update() {
+            var endTime = Date.now();
+
+            audio.removeEventListener('play', update, false);
+            audio.removeEventListener('timeupdate', update, false);
+            audio.pause();
+
+            callback(null, endTime - startTime);
+        }
+
+        audio.addEventListener('play', update, false);
+        audio.addEventListener('timeupdate', update, false);
+
+        startTime = Date.now();
+        audio.play();
+    }
+
+    function audioLatency(callback) {
+        callback = ensureCallback(callback);
+
+        if (!window.Audio) {
+            callback(new Error('Audio not supported'));
+            return;
+        }
+
+        var audio = new window.Audio();
+
+        function onCanPlayThrough() {
+            audio.removeEventListener('canplaythrough', onCanPlayThrough, false);
+
+            // Run the test twice: once for "cold" time, once for "warm" time.
+            getPlayLatency(audio, function (err, coldTime) {
+                if (err) {
+                    callback(err);
+                    return;
+                }
+
+                getPlayLatency(audio, function (err, warmTime) {
+                    if (err) {
+                        callback(err);
+                        return;
+                    }
+
+                    callback(null, {
+                        pass: coldTime <= MAX_LATENCY && warmTime <= MAX_LATENCY,
+                        coldLatency: coldTime,
+                        warmLatency: warmTime
+                    });
+                });
+            });
+        }
+
+        function onError() {
+            callback(new Error('Failed to load audio'));
+        }
+
+        var source = document.createElement('source');
+        source.src = cacheBust.url('assets/silence.wav');
+        source.addEventListener('error', onError, false);
+
+        audio.addEventListener('canplaythrough', onCanPlayThrough, false);
+        audio.addEventListener('error', onError, false);
+        audio.appendChild(source);
+        audio.play();
+
+        // Work around Webkit bug (present in Chrome <= 15, Safari <= 5, at
+        // time of writing) where the browser will decide it doesn't /need/
+        // to download all these pesky audio files.
+        window['audio__' + Math.random()] = audio;
+    }
+
+    return function (callback) {
+        callback = ensureCallback(callback);
+
+        timeout(5000, audioLatency, callback);
+    };
+});