Various fixes for aria-activedescendant.

third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp

Index: third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
diff --git a/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp b/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
index 36a4afcaad658dcc33d08361997dda629950d440..0e68691113381ecaef9955e8a2d8d8af865009b7 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
@@ -143,6 +143,24 @@ void AXNodeObject::alterSliderValue(bool increase)
     axObjectCache().postNotification(getNode(), AXObjectCacheImpl::AXValueChanged);
 }
 
+AXObject* AXNodeObject::activeDescendant() const
+{
+    if (!getNode() || !getNode()->isElementNode())
+        return nullptr;
+
+    const AtomicString& activeDescendantAttr = getAttribute(aria_activedescendantAttr);
+    if (activeDescendantAttr.isNull() || activeDescendantAttr.isEmpty())
+        return nullptr;
+
+    Element* element = toElement(getNode());
+    Element* descendant = element->treeScope().getElementById(activeDescendantAttr);
+    if (!descendant)
+        return nullptr;
+
+    AXObject* axDescendant = axObjectCache().getOrCreate(descendant);
+    return axDescendant;
+}
+
 String AXNodeObject::ariaAccessibilityDescription() const
 {
     String ariaLabelledby = ariaLabelledbyAttribute();
@@ -1065,19 +1083,21 @@ bool AXNodeObject::isRequired() const
 
 bool AXNodeObject::canSetFocusAttribute() const
 {
-    Node* node = this->getNode();
+    Node* node = getNode();
     if (!node)
         return false;
 
     if (isWebArea())
         return true;
 
+    // Children of elements with an aria-activedescendant attribute should be
+    // focusable if they have an ARIA role.
+    if (ariaRoleAttribute() != UnknownRole && ancestorExposesActiveDescendant())
+        return true;
+
     // NOTE: It would be more accurate to ask the document whether setFocusedNode() would
     // do anything. For example, setFocusedNode() will do nothing if the current focused
     // node will not relinquish the focus.
-    if (!node)
-        return false;
-
     if (isDisabledFormControl(node))
         return false;
 
@@ -1100,6 +1120,15 @@ bool AXNodeObject::canSetValueAttribute() const
     return !isReadOnly();
 }
 
+bool AXNodeObject::canSetSelectedAttribute() const
+{
+    // ARIA list box options can be selected if they are children of an element
+    // with an aria-activedescendant attribute.
+    if (ariaRoleAttribute() == ListBoxOptionRole && ancestorExposesActiveDescendant())
+        return true;
+    return AXObject::canSetSelectedAttribute();
+}
+
 bool AXNodeObject::canvasHasFallbackContent() const
 {
     Node* node = this->getNode();