Telemetry media_measurement plus play action and tests.

tools/perf/perf_tools/media_measurement.py

+# Copyright (c) 2013 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.
+
+"""Media measurement class gathers media related metrics on a page set.
+
+Default media metrics are collected for every media element in the page, such as
+decoded_frame_count, dropped_frame_count, decoded_video_bytes, and
+decoded_audio_bytes.
+"""
+
+import os
+
+from telemetry.page import page_measurement
+
+
+class MediaMeasurement(page_measurement.PageMeasurement):
+  """Provide general video and audio metrics."""
+
+  def __init__(self):
+    super(MediaMeasurement, self).__init__('media_metrics')
+
+  def results_are_the_same_on_every_page(self):
+    """Results can vary from page to page based on media events taking place."""
+    return False
+
+  def ReportCollectedMetrics(self, tab, results):
+    """Reports all recorded metrics as Telemetry perf results.
+
+    Metrics are recorded for each media element in the page. Each metric result
+    has media info + metric values as a map, for example:
+    Media metric = {
+      'info': {
+          'src': 'file.webm',
+          'id': 'video1',
+          ...
+      },
+      'metrics': {
+          'ttp': [120, 'ms'],
+          'decoded_bytes': [13233, 'bytes'],
+          ...
+      }
+    }
+    """
+    media_metrics = tab.EvaluateJavaScript('window.__getAllMetrics()')
+    for media_metric in media_metrics:
+      self.AddResult(media_metric, results)
+
+  def AddResult(self, media_metric, results):
+    """Adds the media metric result to global results, needed for graphing."""
+    info = media_metric['info']
+    metrics = media_metric['metrics']
+    for metric in metrics:
+      value, units = GetValueUnit(metrics[metric])
+      trace = GetTraceName(info)
+      results.Add(trace, units, value, chart_name=metric,
+                  data_type='default')
+
+  def LoadDepsJS(self, tab):
+    """Loads the JS files needed for media metrics, if not already loaded."""
+    # Media actions could have already loaded the JS file.

[scherkus (not reviewing), 2013/06/14 20:50:45]

is it possible to always have actions load the JS?

I'm curious whether we can trim down the # of possible ways to load JS to one

[shadi, 2013/06/17 19:13:59]

The problem is that we might run a media measurement without any actions, and we
might run media action outside media measurement tests. So, we need both to load
the JS when needed.

+    deps_found = tab.EvaluateJavaScript('window.__mediaRecorders != undefined')
+    if not deps_found:
+      with open(
+          os.path.join(os.path.dirname(__file__), 'media_metrics.js')) as f:
+        js = f.read()
+        tab.ExecuteJavaScript(js)
+
+  def MeasurePage(self, page, tab, results):
+    """Measure the page's performance."""
+    self.LoadDepsJS(tab)
+    self.ReportCollectedMetrics(tab, results)
+
+
+def GetValueUnit(metric):
+  """Returns a (value, units) pair stored in a metric if available."""
+  if isinstance(metric, (list, tuple)):

[scherkus (not reviewing), 2013/06/14 20:50:45]

what's an example of a metric that has no units? do we generate any unitless
metrics?

would it be better to require JS to always provide units (even if they're
no_unit) so we don't need special casing behaviour here?

[shadi, 2013/06/17 19:13:59]

We don't generate unitless metrics. We can enforce that rule anyway.

+    if len(metric) > 1:
+      return (metric[0], metric[1])
+    else:
+      return (metric[0], 'no_unit')
+  return (metric, 'no_unit')

[scherkus (not reviewing), 2013/06/14 20:50:45]

is no_unit a special unit from telemetry's perspective?

[shadi, 2013/06/17 19:13:59]

No it is not. 

+
+
+def GetTraceName(info):
+  """Returns a media trace name based on the metric info map.
+
+  In order, returns the first available:
+    - 'id' key value.
+    - file name based on 'src' key value.
+    - the first key value available.
+    - 'no_trace'.
+  """
+  if 'id' in info:
+    return info['id']
+  elif 'src' in info:
+    # Return only file name in src.
+    src = info['src']
+    return src[src.rfind('/') + 1:]
+  else:
+    for key in info:
+      return info[key]
+    return 'no_trace'