Fix more closure warnings.

closure.log

@@ -612,10 +612,6 @@ Found    : PolymerElement
             Object.getPrototypeOf(this.prototype).constructor.importPath;
                                   ^^^^^^^^^^^^^^
 
-/polymer.html_script_11.js:573: WARNING - Function Polymer.ResolveUrl.resolveUrl: called with 1 argument(s). Function requires at least 2 argument(s) and at most 2.
-            importPath ? Polymer.ResolveUrl.resolveUrl(importPath) : '';
-                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 /polymer.html_script_11.js:574: WARNING - Invalid type for parameter 1 of function finalizeTemplate.
 Expected : HTMLElement|null
 Found    : Object|null
@@ -665,10 +661,6 @@ Found    : PolymerElement
           window.ShadyCSS.styleSubtree(this, properties);
                                        ^^^^
 
-/polymer.html_script_11.js:764: WARNING - Function Polymer.ResolveUrl.resolveUrl: called with 1 argument(s). Function requires at least 2 argument(s) and at most 2.
-          base = Polymer.ResolveUrl.resolveUrl(this.importPath);
-                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 /polymer.html_script_11.js:779: WARNING - Property _parseTemplateContent never defined on polymerElementBase of type polymerElementBase<|function(new:polymerElementBase):?|>
         return super._parseTemplateContent(template, templateInfo, nodeInfo);
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1415,4 +1407,4 @@ externs/closure-types.js:759: WARNING - property toggle on interface Polymer_Arr
 Polymer_ArraySelectorMixin.prototype.toggle;
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-0 error(s), 309 warning(s), 72.6% typed
+0 error(s), 307 warning(s), 72.6% typed

lib/utils/resolve-url.html

@@ -23,7 +23,7 @@
      *
      * @memberof Polymer.ResolveUrl
      * @param {string} url Input URL to resolve
-     * @param {string} baseURI Base URI to resolve the URL against
+     * @param {string=} baseURI Base URI to resolve the URL against
      * @return {string} resolved URL
      */
     function resolveUrl(url, baseURI) {