WebUI cleanup: Remove cr.icon.getUrlForCss() obsolete workaround.

The code was adding a trailing space when the URL ends with "\", to work around
https://bugs.webkit.org/show_bug.cgi?id=28885 which no longer seems to be an issue.

Bug: None
Test: Run https://jsfiddle.net/m7brn0q4/, verify that a network request to "foo/bar/?\" is sent.
Change-Id: I351d60350ab43b99270edaef063da76b35955a1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1793789
Commit-Queue: Esmael Elmoslimany <aee@chromium.org>
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695242}

ui/webui/resources/js/icon.js

@@ -41,14 +41,8 @@ cr.define('cr.icon', function() {
     // http://www.w3.org/TR/css3-values/#uris
     // Parentheses, commas, whitespace characters, single quotes (') and double
     // quotes (") appearing in a URI must be escaped with a backslash
-    let s2 = s.replace(/(\(|\)|\,|\s|\'|\"|\\)/g, '\\$1');
-    // WebKit has a bug when it comes to URLs that end with \
-    // https://bugs.webkit.org/show_bug.cgi?id=28885
-    if (/\\\\$/.test(s2)) {
-      // Add a space to work around the WebKit bug.
-      s2 += ' ';
-    }
-    return 'url("' + s2 + '")';
+    const s2 = s.replace(/(\(|\)|\,|\s|\'|\"|\\)/g, '\\$1');
+    return `url("${s2}")`;
   }
 
   /**