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

tools/perf/benchmarks/spaceport.py

Index: tools/perf/benchmarks/spaceport.py
diff --git a/tools/perf/benchmarks/spaceport.py b/tools/perf/benchmarks/spaceport.py
index ec46ffb605388b837bea2f1d4e547dc794833e42..db2fca6643cd74cb183e4d56cd0c4a58f77485c9 100644
--- a/tools/perf/benchmarks/spaceport.py
+++ b/tools/perf/benchmarks/spaceport.py
@@ -86,11 +86,13 @@ class _SpaceportMeasurement(page_test.PageTest):
       results.AddValue(scalar.ScalarValue(
           results.current_page, '%s.%s'% (chart, trace),
           'objects (bigger is better)', float(result_dict[key]),
-          important=False, description=DESCRIPTIONS.get(chart)))
+          important=False, description=DESCRIPTIONS.get(chart),
+          higher_is_better=True))
     results.AddValue(list_of_scalar_values.ListOfScalarValues(
         results.current_page, 'Score', 'objects (bigger is better)',
         [float(x) for x in result_dict.values()],
-        description='Combined score for all parts of the spaceport benchmark.'))
+        description='Combined score for all parts of the spaceport benchmark.',
+        higher_is_better=True))
 
 
 # crbug.com/166703: This test frequently times out on Windows.