Add backtick to HTML escape code

Internet Explorer treats a backtick (`) as an attribute
delimiter like " and '. Account for this in HTML escape
code.

Change-Id: I48bccc0013829662479ce321a34f5c69e48aca95

polygerrit-ui/app/scripts/util.js

@@ -30,11 +30,12 @@ util.htmlEntityMap = {
   '>': '>',
   '"': '"',
   '\'': ''',
-  '/': '/'
+  '/': '/',
+  '`': '`',
 };
 
 util.escapeHTML = function(str) {
-  return str.replace(/[&<>"'\/]/g, function(s) {
+  return str.replace(/[&<>"'`\/]/g, function(s) {
     return util.htmlEntityMap[s];
   });
 };