Wrap chemical formulas in LTR marks, see phetsims/chipper#1355

js/util/StringUtils.js

@@ -283,6 +283,28 @@ var StringUtils = {
     return string.replace( /\u202a/g, '[LTR]' ).replace( /\u202b/g, '[RTL]' ).replace( /\u202c/g, '[POP]' );
   },
 
+  /**
+   * Wraps a string with embedding marks for LTR display.
+   * @public
+   *
+   * @param {string} string
+   * @returns {string}
+   */
+  wrapLTR: function( string ) {
+    return LTR + string + POP;
+  },
+
+  /**
+   * Wraps a string with embedding marks for RTL display.
+   * @public
+   *
+   * @param {string} string
+   * @returns {string}
+   */
+  wrapRTL: function( string ) {
+    return LTR + string + POP;
+  },
+
   /**
    * Assert that a template var is in a string. Useful for translated strings with a template var pattern like
    * "Hello {{meanName}}" --> "Hello goofball". See StringUtils.fillIn() for base usages of template var pattern.