Discard hidden articles when using fast path

java/org/chromium/distiller/ContentExtractor.java

Index: java/org/chromium/distiller/ContentExtractor.java
diff --git a/java/org/chromium/distiller/ContentExtractor.java b/java/org/chromium/distiller/ContentExtractor.java
index 4a8f8bd8dbee9acff98fbbc9084f7f5d8b4626fe..9e6c4f60e979672e39d0133ed2de863b4c856811 100644
--- a/java/org/chromium/distiller/ContentExtractor.java
+++ b/java/org/chromium/distiller/ContentExtractor.java
@@ -167,23 +167,40 @@ public class ContentExtractor {
      */
     private Element getArticleElement(Element root) {
         NodeList<Element> allArticles = root.getElementsByTagName("ARTICLE");
+        List<Element> visibleElements = getVisibleElements(allArticles);
         // Having multiple article elements usually indicates a bad case for this shortcut.
         // TODO(wychen): some sites exclude things like title and author in article element.
-        if (allArticles.getLength() == 1) {
-            return allArticles.getItem(0);
+        if (visibleElements.size() == 1) {
+            return visibleElements.get(0);
         }
         // Note that the CSS property matching is case sensitive, and "Article" is the correct
         // capitalization.
         String query = "[itemscope][itemtype*=\"Article\"],[itemscope][itemtype*=\"Post\"]";
         allArticles = DomUtil.querySelectorAll(root, query);
+        visibleElements = getVisibleElements(allArticles);
         // It is commonly seen that the article is wrapped separately or in multiple layers.
-        if (allArticles.getLength() > 0) {
-            return Element.as(DomUtil.getNearestCommonAncestor(allArticles));
+        if (visibleElements.size() > 0) {
+            return Element.as(DomUtil.getNearestCommonAncestor(visibleElements));
         }
         return null;
     }
 
     /**
+     * Get a list of visible elements.
+     * @return A list of visible elements.
+     */
+    private List<Element> getVisibleElements(NodeList<Element> nodeList) {
+        List<Element> visibleElements = new ArrayList<>();
+        for (int i = 0; i < nodeList.getLength(); i++) {
+            Element element = nodeList.getItem(i);
+            if (DomUtil.isVisible(element)) {
+                visibleElements.add(element);
+            }
+        }
+        return visibleElements;
+    }
+
+    /**
      * Converts the original HTML page into a WebDocument for analysis.
      */
     private WebDocumentInfo createWebDocumentInfoFromPage() {