Presubmit test for overriding properties generated by Polymer mixin shim

chrome/browser/web_dev_style/css_checker.py

 # Copyright 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 151 matching lines @@
     def milliseconds_for_small_times(line):
       return small_seconds_reg.search(line)
 
     def suggest_ms_from_s(line):
       ms = int(float(small_seconds_reg.search(line).group(1)) * 1000)
       return ' (replace with %dms)' % ms
 
     def no_data_uris_in_source_files(line):
       return re.search(r'\(\s*\s*data:', line)
 
+    def no_mixin_shims(line):
+      return re.search('\-\-[\w\-]+_\-_[\w\-]+\s*:', line)
+
     def no_quotes_in_url(line):
       return re.search('url\s*\(\s*["\']', line, re.IGNORECASE)
 
     def one_rule_per_line(line):
       one_rule_reg = re.compile(r"""
           [\w-](?<!data):  # a rule: but no data URIs
           (?!//)[^;]+;     # value; ignoring colons in protocols:// and };
           \s*[^ }]\s*      # any non-space after the end colon
           """,
           re.VERBOSE)
@@ skipping 157 matching lines @@
           'test': hex_could_be_shorter,
           'after': suggest_short_hex,
         },
         { 'desc': 'Use milliseconds for time measurements under 1 second.',
           'test': milliseconds_for_small_times,
           'after': suggest_ms_from_s,
         },
         { 'desc': "Don't use data URIs in source files. Use grit instead.",
           'test': no_data_uris_in_source_files,
         },
+        { 'desc': "Don't override custom properties created by Polymer's mixin "
+                  "shim. Set mixins or documented custom properties directly.",
+          'test': no_mixin_shims,
+        },
         { 'desc': "Don't use quotes in url().",
           'test': no_quotes_in_url,
         },
         { 'desc': 'One rule per line (what not to do: color: red; margin: 0;).',
           'test': one_rule_per_line,
         },
         { 'desc': 'One selector per line (what not to do: a, b {}).',
           'test': one_selector_per_line,
           'multiline': True,
         },
@@ skipping 55 matching lines @@
                 error += check['after'](line)
               check_errors.append(error)
           if len(check_errors) > 0:
             file_errors.append('- %s\n%s' %
                 (check['desc'], '\n'.join(check_errors)))
       if file_errors:
         results.append(self.output_api.PresubmitPromptWarning(
             '%s:\n%s' % (f[0], '\n\n'.join(file_errors))))
 
     return results