Make isVisible() faster and more accurate

java/org/chromium/distiller/DomUtil.java

Index: java/org/chromium/distiller/DomUtil.java
diff --git a/java/org/chromium/distiller/DomUtil.java b/java/org/chromium/distiller/DomUtil.java
index d0bcb1bfd7330c1cc8c56be59fdbc6320918284f..dcc96e4de0dcd06290c5c3f42d62963e138e2d25 100644
--- a/java/org/chromium/distiller/DomUtil.java
+++ b/java/org/chromium/distiller/DomUtil.java
@@ -95,11 +95,11 @@ public class DomUtil {
     }-*/;
 
     public static boolean isVisible(Element e) {
-        Style style = getComputedStyle(e);
-        double opacity = JavaScript.parseFloat(style.getOpacity());
-        return !(style.getDisplay().equals("none") ||
-                style.getVisibility().equals("hidden") ||
-                opacity == 0.0F);
+        // Detect whether any of the ancestors has "display: none".
+        // Using offsetParent alone wouldn't work because it's also null when position is fixed.
+        // Using offsetHeight/Width alone makes sense in production, but we have too many
+        // zero-sized elements in our tests.
+        return e.getOffsetParent() != null || e.getOffsetHeight() != 0 || e.getOffsetWidth() != 0;
     }
 
     /*