[Telemetry] Introduce SummarizableValue.

tools/telemetry/telemetry/web_perf/timeline_based_measurement_unittest.py

Index: tools/telemetry/telemetry/web_perf/timeline_based_measurement_unittest.py
diff --git a/tools/telemetry/telemetry/web_perf/timeline_based_measurement_unittest.py b/tools/telemetry/telemetry/web_perf/timeline_based_measurement_unittest.py
index 13ca0f720e98fe3466a06bff6089503e5a6582d6..ae1e5f2684a1a6a269f0dbff128e0caa87efa96f 100644
--- a/tools/telemetry/telemetry/web_perf/timeline_based_measurement_unittest.py
+++ b/tools/telemetry/telemetry/web_perf/timeline_based_measurement_unittest.py
@@ -10,6 +10,7 @@ from telemetry.internal.results import page_test_results
 from telemetry.page import page as page_module
 from telemetry.timeline import async_slice
 from telemetry.timeline import model as model_module
+from telemetry.value import improvement_direction
 from telemetry.value import scalar
 from telemetry.web_perf.metrics import timeline_based_metric
 from telemetry.web_perf import timeline_based_measurement as tbm_module
@@ -19,20 +20,24 @@ class FakeSmoothMetric(timeline_based_metric.TimelineBasedMetric):
 
   def AddResults(self, model, renderer_thread, interaction_records, results):
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'FakeSmoothMetric', 'ms', 1))
+        results.current_page, 'FakeSmoothMetric', 'ms', 1,
+        improvement_direction=improvement_direction.DOWN))
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'SmoothMetricRecords', 'count',
-        len(interaction_records)))
+        len(interaction_records),
+        improvement_direction=improvement_direction.DOWN))
 
 
 class FakeLoadingMetric(timeline_based_metric.TimelineBasedMetric):
 
   def AddResults(self, model, renderer_thread, interaction_records, results):
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'FakeLoadingMetric', 'ms', 2))
+        results.current_page, 'FakeLoadingMetric', 'ms', 2,
+        improvement_direction=improvement_direction.DOWN))
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'LoadingMetricRecords', 'count',
-        len(interaction_records)))
+        len(interaction_records),
+        improvement_direction=improvement_direction.DOWN))
 
 
 class TimelineBasedMetricTestData(object):