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

tools/perf/benchmarks/indexeddb_perf.py

Index: tools/perf/benchmarks/indexeddb_perf.py
diff --git a/tools/perf/benchmarks/indexeddb_perf.py b/tools/perf/benchmarks/indexeddb_perf.py
index e79c2ffcbb3d7d81c9fb76f1910639b1cf7590a3..22b98b119b4a682b82f2998540aa9793194e2dc7 100644
--- a/tools/perf/benchmarks/indexeddb_perf.py
+++ b/tools/perf/benchmarks/indexeddb_perf.py
@@ -30,6 +30,7 @@ from telemetry import page as page_module
 from telemetry.core import util
 from telemetry.page import page_set
 from telemetry.page import page_test
+from telemetry.value import improvement_direction
 from telemetry.value import scalar
 
 _V8_COUNTER_NAMES = [
@@ -80,11 +81,13 @@ class _IndexedDbMeasurement(page_test.PageTest):
         continue
       msec = float(result_dict[key])
       results.AddValue(scalar.ScalarValue(
-          results.current_page, key, 'ms', msec, important=False))
+          results.current_page, key, 'ms', msec, important=False,
+          improvement_direction=improvement_direction.DOWN))
 
       total += msec
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'Total Perf', 'ms', total))
+        results.current_page, 'Total Perf', 'ms', total,
+        improvement_direction=improvement_direction.DOWN))
 
 
   def CustomizeBrowserOptions(self, options):