Implement aria properties setsize and posinset.

Source/modules/accessibility/AXNodeObject.cpp

Index: Source/modules/accessibility/AXNodeObject.cpp
diff --git a/Source/modules/accessibility/AXNodeObject.cpp b/Source/modules/accessibility/AXNodeObject.cpp
index c9294b0ff1f2039b98b16582f4c5c83e50ccc39a..5e59ed1a85c3740e345bfe9fbe707a5dbf8c5e50 100644
--- a/Source/modules/accessibility/AXNodeObject.cpp
+++ b/Source/modules/accessibility/AXNodeObject.cpp
@@ -1172,6 +1172,29 @@ InvalidState AXNodeObject::invalidState() const
     return InvalidStateUndefined;
 }
 
+int AXNodeObject::posInSet() const
+{
+    if (supportsSetSizeAndPosInSet()) {
+        if (hasAttribute(aria_posinsetAttr))
+            return getAttribute(aria_posinsetAttr).toInt();
+        return node()->nodeIndex();

[dmazzoni, 2015/04/10 17:35:21]

Do a null check here.

(The reason this can be null is that AXObjects are reference-counted, so when an
HTML element is destroyed, we get a callback and "detach" the AXObject from its
node (and similarly from layoutObject). The AXObject gets deleted pretty soon
usually, but it's possible that it still exists for a short period of time when
detached so we always need to check if node() and layoutObject() are null.)

+    }
+
+    return 0;
+}
+
+int AXNodeObject::setSize() const
+{
+    if (supportsSetSizeAndPosInSet()) {
+        if (hasAttribute(aria_setsizeAttr))
+            return getAttribute(aria_setsizeAttr).toInt();
+        if (node()->parentNode())
+            return node()->parentNode()->countChildren();

[dmazzoni, 2015/04/10 17:35:21]

I just realized that this isn't going to do the right thing for:

<select>
  <optgroup>
    <option>1</option>
    <option>2</option>
  </optgroup>
  <optgroup>
    <option>3</option>
    <option>4</option>
  </optgroup>
</select>

In this case the DOM tree is more complicated, but the AX tree will be simpler,
it will look more like:

AXMenuListPopup
  AXMenuListOption
  AXMenuListOption
  AXMenuListOption
  AXMenuListOption

or:

AXListBox
  AXListBoxOption
  AXListBoxOption
  AXListBoxOption
  AXListBoxOption

So I think it'd be best to count the children of the AXObject's parent object.

Similarly for posInSet, above - that may mean implementing our own indexInParent
function if it doesn't exist yet.

[shreeramk, 2015/04/13 03:49:59]

Yes it doesn't exist currently.

From blink we can return the attr values of aria_posinset & aria_setsize if
those are present else in chromium side we can call indexinparent and
platformchildcount api to get the required values. Will that not be a good
option?

+    }
+
+    return 0;
+}
+
 String AXNodeObject::ariaInvalidValue() const
 {
     if (invalidState() == InvalidStateOther)