Readdress use_counter_feature_enum issue

tools/metrics/histograms/update_histogram_enum.py

Index: tools/metrics/histograms/update_histogram_enum.py
diff --git a/tools/metrics/histograms/update_histogram_enum.py b/tools/metrics/histograms/update_histogram_enum.py
index f0a29e0fe91c7aaf1c0500e82c572c0d836c4059..3ec3db297764156a14794ab42395f20433c16afb 100644
--- a/tools/metrics/histograms/update_histogram_enum.py
+++ b/tools/metrics/histograms/update_histogram_enum.py
@@ -33,16 +33,27 @@ class UserError(Exception):
     return self.args[0]
 
 
+class DuplicatedValue(Exception):
+  """Exception raised for duplicated enum values.
+
+  Attributes:
+      first_label: First enum label that shares the duplicated enum value.
+      second_label: Second enum label that shares the duplicated enum value.
+  """
+  def __init__(self, first_label, second_label):
+    self.first_label = first_label
+    self.second_label = second_label
+
+
 def Log(message):
   logging.info(message)
 
 
 def ReadHistogramValues(filename, start_marker, end_marker, strip_k_prefix):
-  """Returns a dictionary of enum values and a pair of labels that have the same
-     enum values, read from a C++ file.
+  """Creates a dictionary of enum values, read from a C++ file.
 
   Args:
-      filename: The unix-style path (relative to src/) of the file to open.
+      filename: The unix-style (relative to src/) of the file to open.
       start_marker: A regex that signifies the start of the enum values.
       end_marker: A regex that signifies the end of the enum values.
       strip_k_prefix: Set to True if enum values are declared as kFoo and the
@@ -89,13 +100,13 @@ def ReadHistogramValues(filename, start_marker, end_marker, strip_k_prefix):
         continue
     # If two enum labels have the same value
     if enum_value in result:
-      return result, (result[enum_value], label)
+      raise DuplicatedValue(result[enum_value], label)
     if strip_k_prefix:
       assert label.startswith('k'), "Enum " + label + " should start with 'k'."
       label = label[1:]
     result[enum_value] = label
     enum_value += 1
-  return result, None
+  return result
 
 
 def CreateEnumItemNode(document, value, label):
@@ -183,8 +194,7 @@ def _GetOldAndUpdatedXml(histogram_enum_name, source_enum_values,
 def HistogramNeedsUpdate(histogram_enum_name, source_enum_path, start_marker,
                          end_marker, strip_k_prefix = False):
   """Reads a C++ enum from a .h file and does a dry run of updating
-  histograms.xml to match. Returns true if the histograms.xml file would be
-  changed.
+  histograms.xml to match.
 
   Args:
       histogram_enum_name: The name of the XML <enum> attribute to update.
@@ -194,16 +204,22 @@ def HistogramNeedsUpdate(histogram_enum_name, source_enum_path, start_marker,
       end_marker: A regular expression that matches the end of the C++ enum.
       strip_k_prefix: Set to True if enum values are declared as kFoo and the
           'k' should be stripped.
+
+  Returns:
+      A boolean indicating wheather the histograms.xml file would be changed.
+
+  Raises:
+      DuplicatedValue: An error when two enum labels share the same value.
   """
   Log('Reading histogram enum definition from "{0}".'.format(source_enum_path))
   source_enum_values, duplicated_values = ReadHistogramValues(
       source_enum_path, start_marker, end_marker, strip_k_prefix)

[Ilya Sherman, 2017/04/27 22:23:15]

ReadHistogramValues now only returns the source_enum_values, and does not have a
second duplicated_values return value.  Right?  Please update this code.  (Also,
I already mentioned this in a previous comment.  Please reply 'Done' to
addressed comments, so that it is easier to keep track of what has been
addressed and what hasn't.)

[lunalu1, 2017/04/28 00:31:32]

Done. 

   if duplicated_values:
-    return False, duplicated_values
+    return False
 
   (xml, new_xml) = _GetOldAndUpdatedXml(histogram_enum_name, source_enum_values,
                                         source_enum_path)
-  return xml != new_xml, None
+  return xml != new_xml
 
 
 def UpdateHistogramFromDict(histogram_enum_name, source_enum_values,