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

tools/perf/benchmarks/kraken.py

Index: tools/perf/benchmarks/kraken.py
diff --git a/tools/perf/benchmarks/kraken.py b/tools/perf/benchmarks/kraken.py
index 24498d93764b679161241e77395f79d4919b3479..a1168dcd4f63c30463742a12c78f4ae25211a8d8 100644
--- a/tools/perf/benchmarks/kraken.py
+++ b/tools/perf/benchmarks/kraken.py
@@ -99,7 +99,7 @@ class _KrakenMeasurement(page_test.PageTest):
         continue
       results.AddValue(list_of_scalar_values.ListOfScalarValues(
           results.current_page, key, 'ms', result_dict[key], important=False,
-          description=DESCRIPTIONS.get(key)))
+          description=DESCRIPTIONS.get(key), higher_is_better=False))
       total += _Mean(result_dict[key])
 
     # TODO(tonyg/nednguyen): This measurement shouldn't calculate Total. The
@@ -108,7 +108,8 @@ class _KrakenMeasurement(page_test.PageTest):
         results.current_page, 'Total', 'ms', total,
         description='Total of the means of the results for each type '
                     'of benchmark in [Mozilla\'s Kraken JavaScript benchmark]'
-                    '(http://krakenbenchmark.mozilla.org/)'))
+                    '(http://krakenbenchmark.mozilla.org/)',
+        higher_is_better=False))
 
 
 class Kraken(benchmark.Benchmark):