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

tools/perf/metrics/v8_object_stats.py

Index: tools/perf/metrics/v8_object_stats.py
diff --git a/tools/perf/metrics/v8_object_stats.py b/tools/perf/metrics/v8_object_stats.py
index a085125a91769440be4034be183b29a1518ea911..e6f01668bf0e6fd3e9fa5e9b4d0b1f9bba41d61a 100644
--- a/tools/perf/metrics/v8_object_stats.py
+++ b/tools/perf/metrics/v8_object_stats.py
@@ -6,6 +6,7 @@ import json
 import logging
 
 from metrics import Metric
+from telemetry.value import improvement_direction
 from telemetry.value import scalar
 
 
@@ -230,4 +231,5 @@ class V8ObjectStatsMetric(Metric):
       display_name = counter_name.replace('.', '_')
       results.AddValue(scalar.ScalarValue(
           results.current_page, display_name, 'kb',
-          self._results[counter_name] / 1024.0, description=description))
+          self._results[counter_name] / 1024.0, description=description,
+          improvement_direction=improvement_direction.DOWN))