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

tools/perf/metrics/loading.py

 # Copyright 2013 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.
 
 from metrics import Metric
 from telemetry.value import scalar
 
 class LoadingMetric(Metric):
   """A metric for page loading time based entirely on window.performance"""
 
   def Start(self, page, tab):
     raise NotImplementedError()
 
   def Stop(self, page, tab):
     raise NotImplementedError()
 
   def AddResults(self, tab, results):
     load_timings = tab.EvaluateJavaScript('window.performance.timing')
 
     # NavigationStart relative markers in milliseconds.
     load_start = (
       float(load_timings['loadEventStart']) - load_timings['navigationStart'])
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'load_start', 'ms', load_start))
+        results.current_page, 'load_start', 'ms', load_start,
+        higher_is_better=False))
 
     dom_content_loaded_start = (
       float(load_timings['domContentLoadedEventStart']) -
       load_timings['navigationStart'])
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'dom_content_loaded_start', 'ms',
-        dom_content_loaded_start))
+        dom_content_loaded_start, higher_is_better=False))
 
     fetch_start = (
         float(load_timings['fetchStart']) - load_timings['navigationStart'])
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'fetch_start', 'ms', fetch_start,
-        important=False))
+        important=False, higher_is_better=False))
 
     request_start = (
         float(load_timings['requestStart']) - load_timings['navigationStart'])
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'request_start', 'ms', request_start,
-        important=False))
+        important=False, higher_is_better=False))
 
     # Phase measurements in milliseconds.
     domain_lookup_duration = (
         float(load_timings['domainLookupEnd']) -
         load_timings['domainLookupStart'])
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'domain_lookup_duration', 'ms',
-        domain_lookup_duration, important=False))
+        domain_lookup_duration, important=False, higher_is_better=False))
 
     connect_duration = (
         float(load_timings['connectEnd']) - load_timings['connectStart'])
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'connect_duration', 'ms', connect_duration,
-        important=False))
+        important=False, higher_is_better=False))
 
     request_duration = (
         float(load_timings['responseStart']) - load_timings['requestStart'])
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'request_duration', 'ms', request_duration,
-        important=False))
+        important=False, higher_is_better=False))
 
     response_duration = (
         float(load_timings['responseEnd']) - load_timings['responseStart'])
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'response_duration', 'ms', response_duration,
-        important=False))
+        important=False, higher_is_better=False))