Various fixes for aria-activedescendant.

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

Index: third_party/WebKit/Source/modules/accessibility/AXObject.cpp
diff --git a/third_party/WebKit/Source/modules/accessibility/AXObject.cpp b/third_party/WebKit/Source/modules/accessibility/AXObject.cpp
index fee64c6d8d0827216bf91915953c1d68b30addb7..f219ccaa2831c03906f7656fc988688823078546 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXObject.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXObject.cpp
@@ -330,7 +330,8 @@ const char* ariaWidgets[] = {
     "timer",
     "tooltip",
     "treeitem",
-    // Composite user interface widgets.  This list is also from w3.org site refrerenced above.
+    // Composite user interface widgets.
+    // This list is also from the w3.org site referenced above.
     "combobox",
     "grid",
     "listbox",
@@ -388,6 +389,7 @@ AXObject::AXObject(AXObjectCacheImpl& axObjectCache)
     , m_cachedIsDescendantOfDisabledNode(false)
     , m_cachedHasInheritedPresentationalRole(false)
     , m_cachedIsPresentationalChild(false)
+    , m_cachedAncestorExposesActiveDescendant(false)
     , m_cachedLiveRegionRoot(nullptr)
     , m_axObjectCache(&axObjectCache)
 {
@@ -521,6 +523,7 @@ void AXObject::updateCachedAttributeValuesIfNeeded() const
     m_cachedLiveRegionRoot = isLiveRegion() ?
         this :
         (parentObjectIfExists() ? parentObjectIfExists()->liveRegionRoot() : 0);
+    m_cachedAncestorExposesActiveDescendant = computeAncestorExposesActiveDescendant();
 }
 
 bool AXObject::accessibilityIsIgnoredByDefault(IgnoredReasons* ignoredReasons) const
@@ -676,6 +679,24 @@ bool AXObject::isPresentationalChild() const
     return m_cachedIsPresentationalChild;
 }
 
+bool AXObject::ancestorExposesActiveDescendant() const
+{
+    updateCachedAttributeValuesIfNeeded();
+    return m_cachedAncestorExposesActiveDescendant;
+}
+
+bool AXObject::computeAncestorExposesActiveDescendant() const
+{
+    for (const AXObject* object = this; object; object = object->parentObjectUnignored()) {

[dmazzoni, 2016/04/06 15:51:12]

Should this return true for itself or only for an ancestor? I'd expect it to
only return true if activeDescendant is set on an ancestor, but it actually
returns true for the object it's called on if that object has an
activeDescendant.

Also, I think it should call ancestorExposesActiveDescendant() recursively
because then you can take advantage of memoization and make it log(n) times
faster. So something like this:

    AXObject* parent = parentObjectUnignored();
    if (!parent)
        return false;

    if (parent->supportsActiveDescendant() &&
!parent->getAttribute(aria_activedescendantAttr).isEmpty())
        return true;

    return parent->ancestorExposesActiveDescendant();

+        if (object->supportsActiveDescendant()
+            && !object->getAttribute(aria_activedescendantAttr).isEmpty()) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
 // Simplify whitespace, but preserve a single leading and trailing whitespace character if it's present.
 // static
 String AXObject::collapseWhitespace(const String& str)
@@ -979,6 +1000,32 @@ bool AXObject::ariaPressedIsPresent() const
     return !getAttribute(aria_pressedAttr).isEmpty();
 }
 
+bool AXObject::supportsActiveDescendant() const
+{
+    // According to the ARIA Spec, all ARIA composite widgets, ARIA text boxes
+    // and ARIA groups should be able to expose an active descendant.
+    // Implicitly, <input> and <textarea> elements should also have this ability.
+    switch (ariaRoleAttribute()) {
+    case ComboBoxRole:
+    case GridRole:
+    case GroupRole:
+    case ListBoxRole:
+    case MenuRole:
+    case MenuBarRole:
+    case RadioGroupRole:
+    case RowRole:
+    case SearchBoxRole:
+    case TabListRole:
+    case TextFieldRole:
+    case ToolbarRole:
+    case TreeRole:
+    case TreeGridRole:
+        return true;
+    default:
+        return false;
+    }
+}
+
 bool AXObject::supportsARIAAttributes() const
 {
     return isLiveRegion()