[i18n] escape commas, polymer workaround

ui/base/template_expressions.cc

 // Copyright 2015 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.
 
 #include "ui/base/template_expressions.h"
 
 #include <stddef.h>
 
 #include "base/logging.h"
 #include "base/values.h"
@@ skipping 13 matching lines @@
     switch (c) {
       case '\\':
         out.append("\\\\");
         break;
       case '\'':
         out.append("\\'");
         break;
       case '"':
         out.append("\\\"");
         break;
+      case ',':
+        out.append("\\,");
+        break;
       default:
         out += c;
     }
   }
   return out;
 }
 
 }  // namespace
 
 namespace ui {
@@ skipping 64 matching lines @@
     }
 
     formatted.append(replacement);
 
     current_pos = key_end + sizeof(kKeyClose);
   }
   return formatted;
 }
 
 }  // namespace ui