Drop unused tags from histograms print_style

tools/metrics/histograms/print_style.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.
 
 """Holds the constants for pretty printing histograms.xml."""
 
 import os
 import sys
 
 # Import the metrics/common module for pretty print xml.
 sys.path.append(os.path.join(os.path.dirname(__file__), '..', 'common'))
 import pretty_print_xml
 
 # Desired order for tag and tag attributes. The *_ATTRIBUTE_ORDER maps are also
 # used to determine the validity of tag names.
 # { tag_name: [attribute_name, ...] }
 ATTRIBUTE_ORDER = {
     'affected-histogram': ['name'],
-    'detail': [],
     'details': [],
     'enum': ['name', 'type'],
     'enums': [],
-    # TODO(yiyaoliu): Remove fieldtrial related pieces when it is not used.
-    'fieldtrial': ['name', 'separator', 'ordering'],
     'histogram': ['base', 'name', 'enum', 'units'],
     'histogram-configuration': ['logsource'],
     'histogram_suffixes': ['name', 'separator', 'ordering'],
     'histogram_suffixes_list': [],
     'histograms': [],
     'int': ['value', 'label'],
-    'group': ['name', 'label'],
     'obsolete': [],
     'owner': [],
     'suffix': ['base', 'name', 'label'],
     'summary': [],
-    'with-group': ['name'],
     'with-suffix': ['name'],
 }
 
 # Tag names for top-level nodes whose children we don't want to indent.
 TAGS_THAT_DONT_INDENT = [
     'histogram-configuration',
     'histograms',
     'histogram_suffixes_list',
     'enums',
 ]
@@ skipping 27 matching lines @@
 }
 
 
 def GetPrintStyle():
   """Returns an XmlStyle object for pretty printing histograms."""
   return pretty_print_xml.XmlStyle(ATTRIBUTE_ORDER,
                                    TAGS_THAT_HAVE_EXTRA_NEWLINE,
                                    TAGS_THAT_DONT_INDENT,
                                    TAGS_THAT_ALLOW_SINGLE_LINE,
                                    TAGS_ALPHABETIZATION_RULES)