[Telemetry] Introduce SummarizableValue.

tools/telemetry/telemetry/web_perf/metrics/blob_timeline.py

 # Copyright 2015 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.
 
+from telemetry.value import improvement_direction
 from telemetry.value import list_of_scalar_values
 from telemetry.web_perf.metrics import timeline_based_metric
 
 
 WRITE_EVENT_NAME = 'Registry::RegisterBlob'
 READ_EVENT_NAME = 'BlobRequest'
 
 
 class BlobTimelineMetric(timeline_based_metric.TimelineBasedMetric):
   """BlobTimelineMetric reports timing information about blob storage.
@@ skipping 43 matching lines @@
 
   def _AddWriteResultsInternal(self, events, interactions, results):
     writes = []
     for event in events:
       if (self.IsWriteEvent(event) and
           any(self.IsEventInInteraction(event, interaction)
               for interaction in interactions)):
         writes.append(self.ThreadDurationIfPresent(event))
     if writes:
       results.AddValue(list_of_scalar_values.ListOfScalarValues(
-        page=results.current_page,
-        name='blob-writes',
-        units='ms',
-        values=writes,
-        description='List of durations of blob writes.'))
+          page=results.current_page,
+          name='blob-writes',
+          units='ms',
+          values=writes,
+          description='List of durations of blob writes.',
+          improvement_direction=improvement_direction.DOWN))
     else:
       results.AddValue(list_of_scalar_values.ListOfScalarValues(
-        page=results.current_page,
-        name='blob-writes',
-        units='ms',
-        values=None,
-        none_value_reason='No blob write events found for this interaction.'))
+          page=results.current_page,
+          name='blob-writes',
+          units='ms',
+          values=None,
+          none_value_reason='No blob write events found for this interaction.',
+          improvement_direction=improvement_direction.DOWN))
 
 
   def _AddReadResultsInternal(self, events, interactions, results):
     reads = dict()
     for event in events:
       if (not self.IsReadEvent(event) or
           not any(self.IsEventInInteraction(event, interaction)
                  for interaction in interactions)):
         continue
       # Every blob has unique UUID.  To get the total time for reading
       # a blob, we add up the time of all events with the same blob UUID.
       uuid = event.args['uuid']
       if uuid not in reads:
         reads[uuid] = 0
       reads[uuid] += self.ThreadDurationIfPresent(event)
 
     if reads:
       results.AddValue(list_of_scalar_values.ListOfScalarValues(
-        page=results.current_page,
-        name='blob-reads',
-        units='ms',
-        values=reads.values(),
-        description='List of read times for blobs.'))
+          page=results.current_page,
+          name='blob-reads',
+          units='ms',
+          values=reads.values(),
+          description='List of read times for blobs.',
+          improvement_direction=improvement_direction.DOWN))
     else:
       results.AddValue(list_of_scalar_values.ListOfScalarValues(
-        page=results.current_page,
-        name='blob-reads',
-        units='ms',
-        values=None,
-        none_value_reason='No blob read events found for this interaction.'))
+          page=results.current_page,
+          name='blob-reads',
+          units='ms',
+          values=None,
+          none_value_reason='No blob read events found for this interaction.',
+          improvement_direction=improvement_direction.DOWN))