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

tools/perf/benchmarks/dromaeo.py

Index: tools/perf/benchmarks/dromaeo.py
diff --git a/tools/perf/benchmarks/dromaeo.py b/tools/perf/benchmarks/dromaeo.py
index c5e00c452d946479dd20602df6e232cf4bc4cf71..9cb2e8bc439bcfb44c141f2e8bf256027e83eaac 100644
--- a/tools/perf/benchmarks/dromaeo.py
+++ b/tools/perf/benchmarks/dromaeo.py
@@ -77,7 +77,8 @@ class _DromaeoMeasurement(page_test.PageTest):
       if name == suffix:
         important = True
       results.AddValue(scalar.ScalarValue(
-          results.current_page, Escape(name), 'runs/s', value, important))
+          results.current_page, Escape(name), 'runs/s', value, important,
+          higher_is_better=True))
 
     aggregated = {}
     for data in score: