1 files changed, 36 insertions, 10 deletions
diff --git a/chrome/test/media_router/telemetry/benchmarks/media_router_metric.py b/chrome/test/media_router/telemetry/benchmarks/media_router_metric.py
index 352e386..0439b58 100644
--- a/chrome/test/media_router/telemetry/benchmarks/media_router_metric.py
+++ b/chrome/test/media_router/telemetry/benchmarks/media_router_metric.py
@@ -4,6 +4,7 @@
 
 import json
 
+from telemetry.value import histogram
 from telemetry.value import histogram_util
 from telemetry.value import scalar
 
@@ -27,19 +28,44 @@ HISTOGRAMS_TO_RECORD = [
 class MediaRouterMetric(Metric):
   "A metric for media router dialog latency from histograms."
 
+  def __init__(self):
+    super(MediaRouterMetric, self).__init__()
+    self._histogram_start = dict()
+    self._histogram_delta = dict()
+    self._started = False
+
   def Start(self, page, tab):
-    raise NotImplementedError()
+    self._started = True
+
+    for h in HISTOGRAMS_TO_RECORD:
+      histogram_data = histogram_util.GetHistogram(
+          h['type'], h['name'], tab)
+      # Histogram data may not be available
+      if not histogram_data:
+        continue
+      self._histogram_start[h['name']] = histogram_data
 
   def Stop(self, page, tab):
-    raise NotImplementedError()
+    assert self._started, 'Must call Start() first'
+    for h in HISTOGRAMS_TO_RECORD:
+      # Histogram data may not be available
+      if h['name'] not in self._histogram_start:
+        continue
+      histogram_data = histogram_util.GetHistogram(
+          h['type'], h['name'], tab)
+
+      if not histogram_data:
+        continue
+      self._histogram_delta[h['name']] = histogram_util.SubtractHistogram(
+          histogram_data, self._histogram_start[h['name']])
 
   def AddResults(self, tab, results):
+    assert self._histogram_delta, 'Must call Stop() first'
     for h in HISTOGRAMS_TO_RECORD:
-      result = json.loads(histogram_util.GetHistogram(
-          h['type'], h['name'], tab))
-      if 'sum' in result:
-        # For all the histograms logged here, there's a single entry so sum
-        # is the exact value for that entry.
-        results.AddValue(scalar.ScalarValue(
-            results.current_page, h['display_name'], h['units'],
-            result['sum']))
+      # Histogram data may not be available
+      if h['name'] not in self._histogram_delta:
+        continue
+      results.AddValue(histogram.HistogramValue(
+          results.current_page, h['display_name'], h['units'],
+          raw_value_json=self._histogram_delta[h['name']], important=False,
+          description=h.get('description')))