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

tools/telemetry/telemetry/web_perf/metrics/fast_metric.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging
 
 from telemetry.timeline import bounds
+from telemetry.value import improvement_direction
 from telemetry.value import scalar
 from telemetry.web_perf import timeline_interaction_record as tir_module
 from telemetry.web_perf.metrics import timeline_based_metric
 from telemetry.web_perf.metrics import v8_stats as v8_stats_module
 
 
 class FastMetric(timeline_based_metric.TimelineBasedMetric):
   def __init__(self):
     super(FastMetric, self).__init__()
 
@@ skipping 28 matching lines @@
     Args:
       model: a TimelineModule instance
       renderer_thread: a telemetry.timeline.thread.Thread() instance
       interaction_records: an iterable of TimelineInteractionRecord instances
       results: an instance of page.PageTestResults
     """
     self.VerifyNonOverlappedRecords(interaction_records)
 
     duration = sum(r.end - r.start for r in interaction_records)
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'fast-duration', 'ms', duration))
+        results.current_page, 'fast-duration', 'ms', duration,
+        improvement_direction=improvement_direction.DOWN))
 
     try:
       cpu_time = sum(
           r.GetOverlappedThreadTimeForSlice(s)
           for r in interaction_records
           for s in renderer_thread.toplevel_slices)
     except tir_module.NoThreadTimeDataException:
       logging.warning(
           'Main thread cpu_time cannot be computed for records %s since '
           'trace does not contain thread time data.',
           repr(interaction_records))
     else:
       results.AddValue(scalar.ScalarValue(
-          results.current_page, 'fast-cpu_time', 'ms', cpu_time))
+          results.current_page, 'fast-cpu_time', 'ms', cpu_time,
+          improvement_direction=improvement_direction.DOWN))
 
     idle_time = duration - sum(
         bounds.Bounds.GetOverlap(r.start, r.end, s.start, s.end)
         for r in interaction_records
         for s in renderer_thread.toplevel_slices)
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'fast-idle_time', 'ms', idle_time))
+        results.current_page, 'fast-idle_time', 'ms', idle_time,
+        improvement_direction=improvement_direction.UP))
 
     v8_stats = v8_stats_module.V8Stats(renderer_thread, interaction_records)
 
     for event_stats in v8_stats.all_event_stats:
       results.AddValue(scalar.ScalarValue(
           results.current_page, 'fast-' + event_stats.result_name, 'ms',
           event_stats.thread_duration,
-          event_stats.result_description))
+          event_stats.result_description,
+          improvement_direction=improvement_direction.DOWN))
       results.AddValue(scalar.ScalarValue(
           results.current_page,
           'fast-' + event_stats.result_name + '_outside_idle', 'ms',
           event_stats.thread_duration_outside_idle,
-          event_stats.result_description + 'outside of idle notifications'))
+          event_stats.result_description + 'outside of idle notifications',
+          improvement_direction=improvement_direction.DOWN))
 
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'fast-total_garbage_collection', 'ms',
         v8_stats.total_gc_thread_duration,
-        'Total thread duration of all garbage collection events'))
+        'Total thread duration of all garbage collection events',
+        improvement_direction=improvement_direction.DOWN))
 
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'fast-total_garbage_collection_outside_idle',
         'ms', v8_stats.total_gc_thread_duration_outside_idle,
         'Total thread duration of all garbage collection events outside of idle'
-        'notifications'))
+        'notifications', improvement_direction=improvement_direction.DOWN))