Just remove --css-mixins: {...}; in presubmit checked contents

chrome/browser/web_dev_style/css_checker.py

 # Copyright (c) 2012 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.
 
 """Presubmit script for Chromium WebUI resources.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools, and see
 http://www.chromium.org/developers/web-development-style-guide for the rules
 we're checking against here.
@@ skipping 15 matching lines @@
       return (len(s) == 6 and s[0] == s[1] and s[2] == s[3] and s[4] == s[5])
 
     def _is_gray(s):
       return s[0] == s[1] == s[2] if len(s) == 3 else s[0:2] == s[2:4] == s[4:6]
 
     def _remove_all(s):
       s = _remove_grit(s)
       s = _remove_ats(s)
       s = _remove_comments(s)
       s = _remove_template_expressions(s)
+      s = _remove_mixins(s)
       return s
 
     def _remove_ats(s):
       at_reg = re.compile(r"""
           @(?!\d+x\b)\w+[^'"]*?{  # @at-keyword selector junk {, not @2x
           (.*{.*?})+              # inner { curly } blocks, rules, and selector
           .*?}                    # stuff up to the first end curly }
           """,
           re.DOTALL | re.VERBOSE)
       return at_reg.sub('\\1', s)
 
     def _remove_comments(s):
       return re.sub(re.compile(r'/\*.*?\*/', re.DOTALL), '', s)
 
+    def _remove_mixins(s):
+      return re.sub(re.compile(r'--[\d\w-]+: {.*?};', re.DOTALL), '', s)
+
     def _remove_template_expressions(s):
       return re.sub(re.compile(r'\${[^}]*}', re.DOTALL), '', s)
 
     def _remove_grit(s):
       grit_reg = re.compile(r"""
           <if[^>]+>.*?<\s*/\s*if[^>]*>|  # <if> contents </if>
           <include[^>]+>                 # <include>
           """,
           re.DOTALL | re.VERBOSE)
       return re.sub(grit_reg, '', s)
 
     def _rgb_from_hex(s):
       if len(s) == 3:
         r, g, b = s[0] + s[0], s[1] + s[1], s[2] + s[2]
       else:
         r, g, b = s[0:2], s[2:4], s[4:6]
       return int(r, base=16), int(g, base=16), int(b, base=16)
 
     def _strip_prefix(s):
       return re.sub(r'^-(?:o|ms|moz|khtml|webkit)-', '', s)
 
     def alphabetize_props(contents):
       errors = []
+      # TODO(dbeam): make this smart enough to detect issues in mixins.
       for rule in re.finditer(r'{(.*?)}', contents, re.DOTALL):
         semis = map(lambda t: t.strip(), rule.group(1).split(';'))[:-1]
         rules = filter(lambda r: ': ' in r, semis)
         props = map(lambda r: r[0:r.find(':')], rules)
         if props != sorted(props):
           errors.append('    %s;\n' % (';\n    '.join(rules)))
       return errors
 
     def braces_have_space_before_and_nothing_after(line):
       brace_space_reg = re.compile(r"""
@@ skipping 322 matching lines @@
             '%s:\n%s' % (f[0], '\n\n'.join(file_errors))))
 
     if results:
       # Add your name if you're here often mucking around in the code.
       authors = ['dbeam@chromium.org']
       results.append(self.output_api.PresubmitNotifyResult(
           'Was the CSS checker useful? Send feedback or hate mail to %s.' %
           ', '.join(authors)))
 
     return results