[Presubmit] Make CSS checker ignore '@' inside of strings.

chrome/browser/web_dev_style/css_checker.py

Index: chrome/browser/web_dev_style/css_checker.py
diff --git a/chrome/browser/web_dev_style/css_checker.py b/chrome/browser/web_dev_style/css_checker.py
index 82f4cb5c861d9d098bc1fdae0c66fdb710cdd6b6..495cf983dad811b94ed0c673b4b2a3dd45ebdf7c 100644
--- a/chrome/browser/web_dev_style/css_checker.py
+++ b/chrome/browser/web_dev_style/css_checker.py
@@ -33,9 +33,9 @@ class CSSChecker(object):
 
     def _remove_ats(s):
       at_reg = re.compile(r"""
-          @\w+.*?{    # @at-keyword selector junk {
-          (.*{.*?})+  # inner { curly } blocks, rules, and selector junk
-          .*?}        # stuff up to the first end curly }""",
+          @\w+[^'"]*?{  # @at-keyword selector junk {
+          (.*{.*?})+    # inner { curly } blocks, rules, and selector junk
+          .*?}          # stuff up to the first end curly }""",
           re.DOTALL | re.VERBOSE)
       return at_reg.sub('\\1', s)