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

tools/telemetry/telemetry/value/histogram.py

Index: tools/telemetry/telemetry/value/histogram.py
diff --git a/tools/telemetry/telemetry/value/histogram.py b/tools/telemetry/telemetry/value/histogram.py
index 64fadb0a833773175cee0e62f059748200f16bef..cfc8b4fb5e74604bb85a8fa5644ecb74e46b8a2b 100644
--- a/tools/telemetry/telemetry/value/histogram.py
+++ b/tools/telemetry/telemetry/value/histogram.py
@@ -3,9 +3,10 @@
 # found in the LICENSE file.
 import json
 
-from telemetry import value as value_module
 from telemetry import perf_tests_helper
+from telemetry import value as value_module
 from telemetry.value import histogram_util
+from telemetry.value import summarizable
 
 class HistogramValueBucket(object):
   def __init__(self, low, high, count=0):
@@ -26,12 +27,12 @@ class HistogramValueBucket(object):
       '"high": %i' % self.high,
       '"count": %i' % self.count])
 
-class HistogramValue(value_module.Value):
+class HistogramValue(summarizable.SummarizableValue):
   def __init__(self, page, name, units,
                raw_value=None, raw_value_json=None, important=True,
-               description=None):
+               description=None, improvement_direction=None):
     super(HistogramValue, self).__init__(page, name, units, important,
-                                         description)
+                                         description, improvement_direction)
     if raw_value_json:
       assert raw_value == None, \
              'Don\'t specify both raw_value and raw_value_json'
@@ -54,12 +55,13 @@ class HistogramValue(value_module.Value):
     else:
       page_name = None
     return ('HistogramValue(%s, %s, %s, raw_json_string="%s", '
-            'important=%s, description=%s') % (
+            'important=%s, description=%s, improvement_direction=%s') % (
               page_name,
               self.name, self.units,
               self.ToJSONString(),
               self.important,
-              self.description)
+              self.description,
+              self.improvement_direction)
 
   def GetBuildbotDataType(self, output_context):
     if self._IsImportantGivenOutputIntent(output_context):
@@ -104,6 +106,7 @@ class HistogramValue(value_module.Value):
   def FromDict(value_dict, page_dict):
     kwargs = value_module.Value.GetConstructorKwArgs(value_dict, page_dict)
     kwargs['raw_value'] = value_dict
+    kwargs['improvement_direction'] = value_dict['improvement_direction']
 
     return HistogramValue(**kwargs)
 
@@ -115,7 +118,7 @@ class HistogramValue(value_module.Value):
         v0.page, v0.name, v0.units,
         raw_value_json=histogram_util.AddHistograms(
             [v.ToJSONString() for v in values]),
-        important=v0.important)
+        important=v0.important, improvement_direction=v0.improvement_direction)
 
   @classmethod
   def MergeLikeValuesFromDifferentPages(cls, values,