Telemetry media_measurement plus play action and tests.

tools/perf/perf_tools/media_metrics.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 Metrics class injects and calls JS responsible for recording metrics.
+
+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 logging
+import os
+
+
+class MediaMetrics(object):
+  def __init__(self, tab):
+    with open(
+        os.path.join(os.path.dirname(__file__), 'media_metrics.js')) as f:
+      js = f.read()
+      tab.ExecuteJavaScript(js)
+    self.tab = tab
+
+  def Start(self):
+    """Create the media metrics for all media elements in the document."""
+    self.tab.ExecuteJavaScript('window.__createMediaMetricsForDocument()')
+
+  def StopAndGetResults(self, results):
+    """Reports all recorded metrics as Telemetry perf results."""
+    media_metrics = self.tab.EvaluateJavaScript('window.__getAllMetrics()')
+    for media_metric in media_metrics:
+      self.AddResultForMediaElement(media_metric, results)
+
+  def AddResultForMediaElement(self, media_metric, results):
+    """Reports metrics for one media element.
+
+    Media metrics contain an ID identifying the media element and values:
+    media_metric = {
+      'id': 'video_1',
+      'metrics': {
+          'time_to_play': 120,
+          'decoded_bytes': 13233,
+          ...
+      }
+    }
+    """
+    def AddResult(metric, unit):
+      metrics = media_metric['metrics']
+      if metric in metrics:
+        results.Add(trace, unit, str(metrics[metric]), chart_name=metric,
+                    data_type='default')
+
+    trace = media_metric['id']
+    if not trace:
+      logging.error('Metrics ID is missing in results.')
+      return
+
+    AddResult('time_to_play', 'sec')
+    AddResult('playback_time', 'sec')
+    AddResult('decoded_audio_bytes', 'bytes')
+    AddResult('decoded_video_bytes', 'bytes')
+    AddResult('decoded_frame_count', 'frames')
+    AddResult('dropped_frame_count', 'frames')