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

tools/perf/benchmarks/jetstream.py

Index: tools/perf/benchmarks/jetstream.py
diff --git a/tools/perf/benchmarks/jetstream.py b/tools/perf/benchmarks/jetstream.py
index fffa23a4408632e737c52aa05770c861d2c84cfe..cd3fafdbe8e237ac75642b91429b00b67d4bb22e 100644
--- a/tools/perf/benchmarks/jetstream.py
+++ b/tools/perf/benchmarks/jetstream.py
@@ -63,7 +63,7 @@ class _JetstreamMeasurement(page_test.PageTest):
     for k, v in result.iteritems():
       results.AddValue(list_of_scalar_values.ListOfScalarValues(
           results.current_page, k.replace('.', '_'), 'score', v['result'],
-          important=False))
+          important=False, higher_is_better=True))
       # Collect all test scores to compute geometric mean.
       for i, score in enumerate(v['result']):
         if len(all_score_lists) <= i: