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

tools/perf/benchmarks/maps.py

Index: tools/perf/benchmarks/maps.py
diff --git a/tools/perf/benchmarks/maps.py b/tools/perf/benchmarks/maps.py
index be36d7204036552eeff75e43511d5bd9794f461e..41bb9c0d8652fba9f9fdeba50ac2d7f43d6c41db 100644
--- a/tools/perf/benchmarks/maps.py
+++ b/tools/perf/benchmarks/maps.py
@@ -13,6 +13,7 @@ from telemetry.core import util
 from telemetry.page import page as page_module
 from telemetry.page import page_set as page_set_module
 from telemetry.page import page_test
+from telemetry.value import improvement_direction
 from telemetry.value import scalar
 
 
@@ -28,9 +29,11 @@ class _MapsMeasurement(page_test.PageTest):
     total = re.search('total=([0-9]+)', test_results).group(1)
     render = re.search('render=([0-9.]+),([0-9.]+)', test_results).group(2)
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'total_time', 'ms', total))
+        results.current_page, 'total_time', 'ms', total,
+        improvement_direction=improvement_direction.DOWN))
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'render_mean_time', 'ms', render))
+        results.current_page, 'render_mean_time', 'ms', render,
+        improvement_direction=improvement_direction.DOWN))
 
 class MapsPage(page_module.Page):
   def __init__(self, page_set, base_dir):