Remove obsolete fieldtrial related code.

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 attributes; attributes listed here will appear first,
 # and in the same order as in these lists.
 # { tag_name: [attribute_name, ...] }
 ATTRIBUTE_ORDER = {
   'enum': ['name', 'type'],
   'histogram': ['name', 'enum', 'units'],
   'int': ['value', 'label'],
   'histogram_suffixes': ['name', 'separator', 'ordering'],
   'suffix': ['name', 'label'],
-  # TODO(yiyaoliu): Remove fieldtrial related pieces when it is not used.
-  'fieldtrial': ['name', 'separator', 'ordering'],
-  'group': ['name', 'label'],
   'affected-histogram': ['name'],
-  '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',
-  # TODO(yiyaoliu): Remove fieldtrial related pieces when it is not used.
-  'fieldtrials',
   'enums'
 ]
 
 # Extra vertical spacing rules for special tag names.
 # {tag_name: (newlines_after_open, newlines_before_close, newlines_after_close)}
 TAGS_THAT_HAVE_EXTRA_NEWLINE = {
   'histogram-configuration': (2, 1, 1),
   'histograms': (2, 1, 1),
-  # TODO(yiyaoliu): Remove fieldtrial related pieces when it is not used.
-  'fieldtrials': (2, 1, 1),
+  'histogram': (1, 1, 1),
   'histogram_suffixes_list': (2, 1, 1),
   'histogram_suffixes': (1, 1, 1),
   'enums': (2, 1, 1),
-  'histogram': (1, 1, 1),
   'enum': (1, 1, 1),
-  'fieldtrial': (1, 1, 1),
 }
 
 # Tags that we allow to be squished into a single line for brevity.
 TAGS_THAT_ALLOW_SINGLE_LINE = [
   'summary',
   'int',
   'owner',
 ]
 
 
 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)