[API] Update StyleSheetLoaderSpec

...to reflect asset path details

platform/commonUI/general/src/StyleSheetLoader.js

@@ -37,6 +37,8 @@ define(
          * @param {object[]} stylesheets stylesheet extension definitions
          * @param $document Angular's jqLite-wrapped document element
          * @param {string} activeTheme the theme in use
+         * @param {string} [assetPath] the directory relative to which
+         *        stylesheets will be found
          */
         function StyleSheetLoader(stylesheets, $document, activeTheme, assetPath) {
             var head = $document.find('head'),
@@ -69,6 +71,8 @@ define(
                     stylesheet.theme === activeTheme;
             }
 
+            assetPath = assetPath || ".";
+
             // Add all stylesheets from extensions
             stylesheets.filter(matchesTheme).forEach(addStyleSheet);
         }