[Telemetry] Rename translate_common_values + add none_value/description support

telemetry/telemetry/value/common_value_helpers.py

Index: telemetry/telemetry/value/common_value_helpers.py
diff --git a/telemetry/telemetry/value/translate_common_values.py b/telemetry/telemetry/value/common_value_helpers.py
similarity index 83%
rename from telemetry/telemetry/value/translate_common_values.py
rename to telemetry/telemetry/value/common_value_helpers.py
index 4aadcd1dc68a0d465c39173f96dfb079e93ca867..72f4bc9922ab130952b355f9d579b018276e4bc8 100644
--- a/telemetry/telemetry/value/translate_common_values.py
+++ b/telemetry/telemetry/value/common_value_helpers.py
@@ -12,7 +12,11 @@ def TranslateMreFailure(mre_failure, page):
 
 def TranslateScalarValue(scalar_value, page):
   assert IsScalarNumericValue(scalar_value)
-  scalar_value['value'] = scalar_value['numeric']['value']
+
+  value = scalar_value['numeric']['value']
+  scalar_value['value'] = value
+  if value is None:
+    scalar_value['none_value_reason'] = 'Common scalar contained None'
 
   name = scalar_value['grouping_keys']['name']
 
@@ -21,6 +25,8 @@ def TranslateScalarValue(scalar_value, page):
     raise ValueError('Must specify improvement direction for value ' + name)
 
   scalar_value['units'] = unit_parts[0]
+  scalar_value['description'] = scalar_value.get('options', {}).get(
+      'description')
 
   if unit_parts[1] == 'biggerIsBetter':
     scalar_value['improvement_direction'] = improvement_direction.UP