Create and display "comparison statistics" to compare two statistics

tools/telemetry/telemetry/page/page_measurement_value.py

Index: tools/telemetry/telemetry/page/page_measurement_value.py
diff --git a/tools/telemetry/telemetry/page/page_measurement_value.py b/tools/telemetry/telemetry/page/page_measurement_value.py
index c2c8e0e09128d995fde035631a6eb7302e10171a..f2630aaaa22375855054b88047dd1a37ea2bcebd 100644
--- a/tools/telemetry/telemetry/page/page_measurement_value.py
+++ b/tools/telemetry/telemetry/page/page_measurement_value.py
@@ -6,6 +6,18 @@ from telemetry.page import perf_tests_helper
 def _Mean(l):
   return float(sum(l)) / len(l) if len(l) > 0 else 0.0
 
+def MeasurementName(chart_name, trace_name):
+  if chart_name:
+    return '%s.%s' % (chart_name, trace_name)
+  else:
+    return trace_name
+
+def ChartTraceFromMeasurement(measurement_name):
+  if "." in measurement_name:
+    return measurement_name.split('.', 1)
+  else:
+    return ('', measurement_name)
+
 class PageMeasurementValue(object):
   def __init__(self, trace_name, units, value, chart_name, data_type):
     self.trace_name = trace_name
@@ -16,10 +28,7 @@ class PageMeasurementValue(object):
 
   @property
   def measurement_name(self):
-    if self.chart_name:
-      return '%s.%s' % (self.chart_name, self.trace_name)
-    else:
-      return self.trace_name
+    return MeasurementName(self.chart_name, self.trace_name)
 
   @property
   def output_value(self):