Add new PyAuto test for measuring audio tag latency.

chrome/test/functional/media/audio_latency_perf.py

Index: chrome/test/functional/media/audio_latency_perf.py
diff --git a/chrome/test/functional/media/audio_latency_perf.py b/chrome/test/functional/media/audio_latency_perf.py
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+++ b/chrome/test/functional/media/audio_latency_perf.py
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+#!/usr/bin/env python
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Audio latency performance test.
+
+Benchmark measuring how fast we can continuously repeat a short sound clip.  In
+the ideal scenario we'd have zero latency processing script, seeking back to the
+beginning of the clip, and resuming audio playback.
+
+Performance is recorded as the average latency of N playbacks.  I.e., if we play
+a clip 50 times and the ideal duration of all playbacks is 1000ms and the total
+duration is 1500ms, the recorded result is (1500ms - 1000ms) / 50 == 10ms.
+"""
+import os
+
+import pyauto_media
+import pyauto_utils
+import pyauto
+
+
+# HTML test path; relative to src/chrome/test/data.
+_TEST_HTML_PATH = os.path.join('media', 'html', 'audio_latency_perf.html')
+
+
+class AudioLatencyPerfTest(pyauto.PyUITest):
+  """PyAuto test container.  See file doc string for more information."""
+
+  def testAudioLatency(self):
+    """Launches HTML test which runs the audio latency test."""
+    self.NavigateToURL(self.GetFileURLForDataPath(_TEST_HTML_PATH))
+
+    # Block until the test finishes and notifies us.
+    self.assertTrue(self.ExecuteJavascript('startTest(true);'))
+    latency = float(self.GetDOMValue('averageLatency'))
+    pyauto_utils.PrintPerfResult('audio_latency', 'latency', latency, 'ms')
+
+
+if __name__ == '__main__':
+  pyauto_media.Main()