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

tools/perf/metrics/media.py

Index: tools/perf/metrics/media.py
diff --git a/tools/perf/metrics/media.py b/tools/perf/metrics/media.py
index 6680d8487d4738b5a83ee655096aa461d1218804..701f509dbeb5aa3df9b9850e1da4903afcad0245 100644
--- a/tools/perf/metrics/media.py
+++ b/tools/perf/metrics/media.py
@@ -5,6 +5,7 @@ import logging
 import os
 
 from metrics import Metric
+from telemetry.value import improvement_direction
 from telemetry.value import list_of_scalar_values
 from telemetry.value import scalar
 
@@ -59,7 +60,7 @@ class MediaMetric(Metric):
       }
     }
     """
-    def AddOneResult(metric, unit):
+    def AddOneResult(metric, unit, direction):
       if metric in exclude_metrics:
         return
 
@@ -72,11 +73,11 @@ class MediaMetric(Metric):
             results.AddValue(list_of_scalar_values.ListOfScalarValues(
                 results.current_page, trace_name, unit,
                 values=[float(v) for v in metrics[m]],
-                important=True))
+                important=True, improvement_direction=direction))
           else:
             results.AddValue(scalar.ScalarValue(
                 results.current_page, trace_name, unit, value=float(metrics[m]),
-                important=True))
+                important=True, improvement_direction=direction))
 
     trace = media_metric['id']
     if not trace:
@@ -84,13 +85,13 @@ class MediaMetric(Metric):
       return
 
     if not self._skip_basic_metrics:
-      AddOneResult('buffering_time', 'ms')
-      AddOneResult('decoded_audio_bytes', 'bytes')
-      AddOneResult('decoded_video_bytes', 'bytes')
-      AddOneResult('decoded_frame_count', 'frames')
-      AddOneResult('dropped_frame_count', 'frames')
-      AddOneResult('time_to_play', 'ms')
+      AddOneResult('buffering_time', 'ms', improvement_direction.DOWN)
+      AddOneResult('decoded_audio_bytes', 'bytes', improvement_direction.DOWN)
+      AddOneResult('decoded_video_bytes', 'bytes', improvement_direction.DOWN)
+      AddOneResult('decoded_frame_count', 'frames', improvement_direction.DOWN)
+      AddOneResult('dropped_frame_count', 'frames', improvement_direction.DOWN)
+      AddOneResult('time_to_play', 'ms', improvement_direction.DOWN)
 
-    AddOneResult('avg_loop_time', 'ms')
-    AddOneResult('seek', 'ms')
+    AddOneResult('avg_loop_time', 'ms', improvement_direction.DOWN)
+    AddOneResult('seek', 'ms', improvement_direction.DOWN)
     return trace