web_dev_style: fix bug in which $i18n{camelCaseKeys} trips presubmit

There's a rule in the web styleguide[1] about CSS .classes-use-dashes.
Our brilliant presubmit uses regex and is silly. So strip $i18n{...}
from the cases that have it so the presubmit still works, but just don't
show line contents in those cases.

[1] https://chromium.googlesource.com/chromium/src/+/master/styleguide/web/web.md

Bug: None
Change-Id: Ic5aaa0caa3087465b6b40946e113b52ddf635f8c
Reviewed-on: https://chromium-review.googlesource.com/785795
Commit-Queue: Dan Beam (no longer on Chrome) <dbeam@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519567}

tools/web_dev_style/html_checker.py

@@ -16,13 +16,20 @@ class HtmlChecker(object):
     self.file_filter = file_filter
 
   def ClassesUseDashFormCheck(self, line_number, line):
-    regex = self.input_api.re.compile("""
+    msg = "Classes should use dash-form."
+    re = self.input_api.re
+    class_regex = re.compile("""
         (?:^|\s)                    # start of line or whitespace
         (class="[^"]*[A-Z_][^"]*")  # class contains caps or '_'
         """,
-        self.input_api.re.VERBOSE)
-    return regex_check.RegexCheck(self.input_api.re, line_number, line, regex,
-        "Classes should use dash-form.")
+        re.VERBOSE)
+
+    # $i18n{...} messes with highlighting. Special path for this.
+    if "$i18n{" in line:
+      match = re.search(class_regex, re.sub("\$i18n{[^}]+}", "", line))
+      return "  line %d: %s" % (line_number, msg) if match else ""
+
+    return regex_check.RegexCheck(re, line_number, line, class_regex, msg)
 
   def DoNotCloseSingleTagsCheck(self, line_number, line):
     regex = r"(/>)"

tools/web_dev_style/html_checker_test.py

@@ -52,6 +52,7 @@ class HtmlCheckerTest(SuperMoxTestBase):
       ' class="abc" ',
       'class="foo-bar"',
       '<div class="foo-bar" id="classBar"',
+      '<div class="foo $i18n{barBazQux}" id="classBar"',
     ]
     for line in lines:
       self.ShouldPassCheck(line, self.checker.ClassesUseDashFormCheck)