Make ComputedStyle generation deterministic.

third_party/WebKit/Source/build/scripts/make_computed_style_base.py

 #!/usr/bin/env python
 # Copyright 2016 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.
 
 import math
 import sys
 
 import json5_generator
 import template_expander
 import make_style_builder
 
 from name_utilities import (
     enum_for_css_keyword, enum_type_name, enum_value_name, class_member_name, method_name
 )
+from collections import OrderedDict
 
 
 # Temporary hard-coded list of fields that are not CSS properties.
 # TODO(shend): Put this into its own JSON5 file.
 NONPROPERTIES = [
     {'name': 'IsLink', 'field_template': 'monotonic_flag',
      'inherited': False, 'independent': False},
     {'name': 'OriginalDisplay', 'field_template': 'keyword', 'initial_keyword': 'inline',
      'type_name': 'EDisplay', 'inherited': False, 'independent': False,
      'keywords': [
@@ skipping 105 matching lines @@
     """
     include_paths = set()
     for property_ in properties:
         if property_['field_type_path'] is not None:
             include_paths.add(property_['field_type_path'] + '.h')
     return list(sorted(include_paths))
 
 
 def _create_enums(properties):
     """
-    Returns a dictionary of enums to be generated, enum name -> [list of enum values]
+    Returns an OrderedDict of enums to be generated, enum name -> [list of enum values]
     """
     enums = {}
     for property_ in properties:
         # Only generate enums for keyword properties that use the default field_type_path.
         if property_['field_template'] == 'keyword' and property_['field_type_path'] is None:
             enum_name = property_['type_name']
             enum_values = [enum_value_name(k) for k in property_['keywords']]
 
             if enum_name in enums:
                 # There's an enum with the same name, check if the enum values are the same
                 assert set(enums[enum_name]) == set(enum_values), \
                     ("'" + property_['name'] + "' can't have type_name '" + enum_name + "' "
                      "because it was used by a previous property, but with a different set of keywords. "
                      "Either give it a different name or ensure the keywords are the same.")
 
             enums[enum_name] = enum_values
 
-    return enums
+    # Return the enums sorted by key (enum name)
+    return OrderedDict(sorted(enums.items(), key=lambda t: t[0]))
 
 
 def _create_field(field_role, property_):
     """
     Create a property or nonproperty field.
     """
     assert field_role in ('property', 'nonproperty')
 
     name_for_methods = property_['name_for_methods']
 
@@ skipping 71 matching lines @@
     # padding, group fields into buckets so that as many buckets as possible
     # are exactly 32 bits. Although this greedy approach may not always
     # produce the optimal solution, we add a static_assert to the code to
     # ensure ComputedStyleBase results in the expected size. If that
     # static_assert fails, this code is falling into the small number of
     # cases that are suboptimal, and may need to be rethought.
     # For more details on packing bitfields to reduce padding, see:
     # http://www.catb.org/esr/structure-packing/#_bitfields
     field_buckets = []
     # Consider fields in descending order of size to reduce fragmentation
-    # when they are selected.
-    for field in sorted(fields, key=lambda f: f.size, reverse=True):
+    # when they are selected. Ties broken in alphabetical order by name.
+    for field in sorted(fields, key=lambda f: (-f.size, f.name)):
         added_to_bucket = False
         # Go through each bucket and add this field if it will not increase
         # the bucket's size to larger than 32 bits. Otherwise, make a new
         # bucket containing only this field.
         for bucket in field_buckets:
             if sum(f.size for f in bucket) + field.size <= 32:
                 bucket.append(field)
                 added_to_bucket = True
                 break
         if not added_to_bucket:
@@ skipping 104 matching lines @@
                     'mapping': [(enum_value_name(k), enum_for_css_keyword(k)) for k in property_['keywords']],
                 }
 
         return {
             'include_paths': self._include_paths,
             'mappings': mappings,
         }
 
 if __name__ == '__main__':
     json5_generator.Maker(ComputedStyleBaseWriter).main()