code: @Nonnull
    public static String unescapeURL (@Nonnull final String sEscapedURL)
    {
      int nIndex = sEscapedURL.indexOf (URL_ESCAPE_CHAR);
      if (nIndex < 0)
      {
        // No escape sequence found
        return sEscapedURL;
      }
  
      final StringBuilder aSB = new StringBuilder (sEscapedURL.length ());
      int nPrevIndex = 0;
      do
      {
        // Append everything before the first quote char
        aSB.append (sEscapedURL, nPrevIndex, nIndex);
        // Append the quoted char itself
        aSB.append (sEscapedURL, nIndex + 1, nIndex + 2);
        // The new position to start searching
        nPrevIndex = nIndex + 2;
        // Search the next escaped char
        nIndex = sEscapedURL.indexOf (URL_ESCAPE_CHAR, nPrevIndex);
      } while (nIndex >= 0);
      // Append the rest
      aSB.append (sEscapedURL.substring (nPrevIndex));
      return aSB.toString ();
    }
docs: Unescape all escaped characters in a CSS URL. All characters masked with a
  '\\' character replaced.
  
  @param sEscapedURL
  The escaped URL. May not be <code>null</code>!
  @return The unescaped URL or the original string, if not a single escape
  sequence is found.