Fix test under shadydom. Slight logic refactor.

Author: kevinpschaaf

lib/mixins/element-mixin.html

@@ -414,11 +414,8 @@
             this._importPath = meta.url.slice(0, meta.url.lastIndexOf('/') + 1);
           } else {
             const module = Polymer.DomModule && Polymer.DomModule.import(/** @type {PolymerElementConstructor} */ (this).is);
-            if (module) {
-              this._importPath = module ? module.assetpath : '';
-            } else {
-              this._importPath = Object.getPrototypeOf(/** @type {PolymerElementConstructor}*/ (this).prototype).constructor.importPath;
-            }
+            this._importPath = (module && module.assetpath) || 
+              Object.getPrototypeOf(/** @type {PolymerElementConstructor}*/ (this).prototype).constructor.importPath;
           }
         }
         return this._importPath;

test/unit/resolveurl.html

@@ -58,7 +58,7 @@
         var resolvedUrl = new RegExp(`${folder}/foo\\.z`);
         var styleHashUrl = /url\('#bar'\)/;
         var styleAbsUrl = /url\('\/zot'\)/;
-        var style = el.shadowRoot.querySelector('style') || document.querySelector('style[scope=p-r]');
+        var style = el.shadowRoot.querySelector('style') || document.querySelector(`style[scope=${elementName}]`);
         assert.match(style.textContent, resolvedUrl, 'url not relative to main document');
         assert.match(style.textContent, styleHashUrl, 'hash url incorrectly resolved');
         assert.match(style.textContent, styleAbsUrl, 'absolute url incorrectly resolved');