Merge r222536 - Web Automation: overflow:hidden elements with no chil…

…dren are mistakenly reported as not visible

https://bugs.webkit.org/show_bug.cgi?id=177514
<rdar://problem/31936291>

Reviewed by Joseph Pecoraro.

* UIProcess/Automation/atoms/ElementDisplayed.js:
(isShown.isElementSubtreeHiddenByOverflow):
Array.prototype.every returns true when passed an empty list, so we need
to check for the case where the element has no children and return 'false'.

Source/WebKit/ChangeLog

@@ -1,3 +1,16 @@
+2017-09-26  Brian Burg  <bburg@apple.com>
+
+        Web Automation: overflow:hidden elements with no children are mistakenly reported as not visible
+        https://bugs.webkit.org/show_bug.cgi?id=177514
+        <rdar://problem/31936291>
+
+        Reviewed by Joseph Pecoraro.
+
+        * UIProcess/Automation/atoms/ElementDisplayed.js:
+        (isShown.isElementSubtreeHiddenByOverflow):
+        Array.prototype.every returns true when passed an empty list, so we need
+        to check for the case where the element has no children and return 'false'.
+
 2017-09-26  Brent Fulgham  <bfulgham@apple.com>
 
         Harden our access to the vector of URL schemes.

Source/WebKit/UIProcess/Automation/atoms/ElementDisplayed.js

@@ -132,6 +132,9 @@ function isShown(element) {
         if (!elementOverflowsContainer(element))
             return false;
 
+        if (!element.childNodes.length)
+            return false;
+
         // This element's subtree is hidden by overflow if all child subtrees are as well.
         return Array.from(element.childNodes).every((childNode) => {
             // Returns true if the child node is overflowed or otherwise hidden.