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 de3bfcfee2f5e60cae13930261ac6164c19d3227..4ca0374a873df26a182c12fe63d6848e51cf556c 100644
--- a/tools/perf/benchmarks/kraken.py
+++ b/tools/perf/benchmarks/kraken.py
@@ -11,6 +11,7 @@ from telemetry import benchmark
 from telemetry import page as page_module
 from telemetry.page import page_set
 from telemetry.page import page_test
+from telemetry.value import improvement_direction
 from telemetry.value import list_of_scalar_values
 from telemetry.value import scalar
 
@@ -100,7 +101,8 @@ 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),
+          improvement_direction=improvement_direction.DOWN))
       total += _Mean(result_dict[key])
 
     # TODO(tonyg/nednguyen): This measurement shouldn't calculate Total. The
@@ -109,7 +111,8 @@ 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/)',
+        improvement_direction=improvement_direction.DOWN))
 
 
 class Kraken(benchmark.Benchmark):