js atoms: Ensure element with overflow state 'hidden' is considered hidden if

all its children have zero size.
On behalf of Google engineers.

Author: sevaseva

javascript/atoms/dom.js

@@ -663,7 +663,8 @@ bot.dom.isShown = function(elem, opt_ignoreOpacity) {
   function hiddenByOverflow(e) {
     return bot.dom.getOverflowState(e) == bot.dom.OverflowState.HIDDEN &&
         goog.array.every(e.childNodes, function(n) {
-          return !bot.dom.isElement(n) || hiddenByOverflow(n);
+          return !bot.dom.isElement(n) || hiddenByOverflow(n) ||
+                 !positiveSize(n);
         });
   }
   return !hiddenByOverflow(elem);

javascript/atoms/test/shown_test.html

@@ -338,6 +338,15 @@
       assertFalse(isShown(target));
     }
 
+    function testOverflowHiddenWithFixedPositionChild() {
+      var target = findElement({id: 'overflowHiddenWithFixedPositionChild'});
+      var child = findElement({id: 'fixedPositionChild'});
+      child.innerHTML = '';
+      assertFalse(isShown(target));
+      child.innerHTML = 'some content';
+      assertTrue(isShown(target));
+    }
+
     function testThatElementIsShownWithZIndex() {
       assertTrue(isShown(findElement({id: 'bug5109'})));
     }
@@ -532,6 +541,13 @@
   This is a zero height/width div and overflow hidden
 </div>
 
+<div style="overflow:hidden; height:0; width:0;">
+  <div id="overflowHiddenWithFixedPositionChild">
+    This is a zero height/width div and overflow hidden
+    <div id="fixedPositionChild" style="position:fixed"></div>
+  </div>
+</div>
+
 <div style="position:relative;
             width:300px;
             height:300px;