Added support for improvement_direction to relevant values, which is propogated to chartjson.

tools/perf/benchmarks/media.py

 # Copyright 2014 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 measurements import media
 import page_sets
 from telemetry import benchmark
 from telemetry.page import page_test
+from telemetry.value import improvement_direction
 from telemetry.value import list_of_scalar_values
 from telemetry.value import scalar
 
 
 class _MSEMeasurement(page_test.PageTest):
   def __init__(self):
     super(_MSEMeasurement, self).__init__(
         action_name_to_run='RunPageInteractions')
 
   def ValidateAndMeasurePage(self, page, tab, results):
     media_metric = tab.EvaluateJavaScript('window.__testMetrics')
     trace = media_metric['id'] if 'id' in media_metric else None
     metrics = media_metric['metrics'] if 'metrics' in media_metric else []
     for m in metrics:
       trace_name = '%s.%s' % (m, trace)
       if isinstance(metrics[m], list):
         results.AddValue(list_of_scalar_values.ListOfScalarValues(
                 results.current_page, trace_name, units='ms',
                 values=[float(v) for v in metrics[m]],
-                important=True))
+                important=True,
+                improvement_direction=improvement_direction.DOWN))
 
       else:
         results.AddValue(scalar.ScalarValue(
                 results.current_page, trace_name, units='ms',
-                value=float(metrics[m]), important=True))
+                value=float(metrics[m]), important=True,
+                improvement_direction=improvement_direction.DOWN))
 
 
 @benchmark.Disabled('android')
 class Media(benchmark.Benchmark):
   """Obtains media metrics for key user scenarios."""
   test = media.Media
   page_set = page_sets.ToughVideoCasesPageSet
 
 
 @benchmark.Disabled
@@ skipping 46 matching lines @@
 class MediaSourceExtensions(benchmark.Benchmark):
   """Obtains media metrics for key media source extensions functions."""
   test = _MSEMeasurement
   page_set = page_sets.MseCasesPageSet
 
   def CustomizeBrowserOptions(self, options):
     # Needed to allow XHR requests to return stream objects.
     options.AppendExtraBrowserArgs(
         ['--enable-experimental-web-platform-features',
          '--disable-gesture-requirement-for-media-playback'])