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

tools/telemetry/telemetry/value/__init__.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.
 """
 The Value hierarchy provides a way of representing the values measurements
 produce such that they can be merged across runs, grouped by page, and output
 to different targets.
 
 The core Value concept provides the basic functionality:
 - association with a page, may be none
@@ skipping 24 matching lines @@
 # value is being interpreted actually affects the conversion. This is insane,
 # but there you have it. There are three contexts in which Values are converted
 # for use by buildbot, represented by these output-intent values.
 PER_PAGE_RESULT_OUTPUT_CONTEXT = 'per-page-result-output-context'
 COMPUTED_PER_PAGE_SUMMARY_OUTPUT_CONTEXT = 'merged-pages-result-output-context'
 SUMMARY_RESULT_OUTPUT_CONTEXT = 'summary-result-output-context'
 
 class Value(object):
   """An abstract value produced by a telemetry page test.
   """
-  def __init__(self, page, name, units, important, description):
+  def __init__(
+      self, page, name, units, important, description, higher_is_better=None):
     """A generic Value object.
 
     Args:
       page: A Page object, may be given as None to indicate that the value
           represents results for multiple pages.
       name: A value name string, may contain a dot. Values from the same test
           with the same prefix before the dot may be considered to belong to
           the same chart.
       units: A units string.
       important: Whether the value is "important". Causes the value to appear
           by default in downstream UIs.
       description: A string explaining in human-understandable terms what this
           value represents.
+      higher_is_better: Whether a higher value is an improvement (True) or a
+          regression (False). None if unknown.

[tonyg, 2014/12/18 17:31:35]

Thinking aloud here... not all Value subclasses have a strict numerical
representation -- for instance FailureValue, StringValue, TraceValue. So that
suggests that higher_is_better doesn't belong in the Value class. There's
probably a variety of solutions, but maybe we're missing a SummarizableValue
class in the hierarchy? The thing to figure out then is whether the stuff in
Summary moves into SummarizableValue or whether it asserts that it only operates
on SummarizableValues (I haven't explored the relationship enough to make a
suggestion).

     """
     self.page = page
     self.name = name
     self.units = units
     self.important = important
     self.description = description
+    self.higher_is_better = higher_is_better
 
   def IsMergableWith(self, that):
     return (self.units == that.units and
             type(self) == type(that) and
             self.important == that.important)
 
   @classmethod
   def MergeLikeValuesFromSamePage(cls, values):
     """Combines the provided list of values into a single compound value.
 
@@ skipping 107 matching lines @@
       'units': self.units,
       'important': self.important
     }
 
     if self.description:
       d['description'] = self.description
 
     if self.page:
       d['page_id'] = self.page.id
 
+    if self.higher_is_better is not None:
+      d['higher_is_better'] = self.higher_is_better
+
     return d
 
   def AsDictWithoutBaseClassEntries(self):
     full_dict = self.AsDict()
     base_dict_keys = set(self._AsDictImpl().keys())
 
     # Extracts only entries added by the subclass.
     return dict([(k, v) for (k, v) in full_dict.iteritems()
                   if k not in base_dict_keys])
 
@@ skipping 63 matching lines @@
       d['description'] = None
 
     page_id = value_dict.get('page_id', None)
     if page_id:
       d['page'] = page_dict[int(page_id)]
     else:
       d['page'] = None
 
     d['important'] = False
 
+    if 'higher_is_better' in value_dict:
+      d['higher_is_better'] = value_dict['higher_is_better']
+
     return d
 
 def ValueNameFromTraceAndChartName(trace_name, chart_name=None):
   """Mangles a trace name plus optional chart name into a standard string.
 
   A value might just be a bareword name, e.g. numPixels. In that case, its
   chart may be None.
 
   But, a value might also be intended for display with other values, in which
   case the chart name indicates that grouping. So, you might have
@@ skipping 14 matching lines @@
   whereas telemetry represents values with a chart_name.trace_name convention,
   where chart_name is optional. This convention is also used by chart_json.
 
   This converts from the telemetry convention to the buildbot convention,
   returning a 2-tuple (measurement_name, trace_name).
   """
   if '.' in value_name:
     return value_name.split('.', 1)
   else:
     return value_name, value_name