Fix for bug CORBA error on getAttributes() for document frame, r=ginn.chen

accessible/src/base/nsDocAccessible.cpp

@@ -456,6 +456,15 @@ NS_IMETHODIMP nsDocAccessible::GetParent(nsIAccessible **aParent)
   return mParent ? nsAccessible::GetParent(aParent) : NS_ERROR_FAILURE;
 }
 
+NS_IMETHODIMP
+nsDocAccessible::GetAttributes(nsIPersistentProperties **aAttributes)
+{
+  NS_ENSURE_ARG_POINTER(aAttributes);
+  *aAttributes = nsnull;
+
+  return mDOMNode ? NS_OK : NS_ERROR_FAILURE;
+}
+
 NS_IMETHODIMP nsDocAccessible::Init()
 {
   PutCacheEntry(gGlobalDocAccessibleCache, mWeakShell, this);

accessible/src/base/nsDocAccessible.h

@@ -81,6 +81,7 @@ class nsDocAccessible : public nsHyperTextAccessible,
     NS_IMETHOD GetState(PRUint32 *aState, PRUint32 *aExtraState);
     NS_IMETHOD GetFocusedChild(nsIAccessible **aFocusedChild);
     NS_IMETHOD GetParent(nsIAccessible **aParent);
+    NS_IMETHOD GetAttributes(nsIPersistentProperties **aAttributes);
     NS_IMETHOD TakeFocus(void);
 
     // ----- nsIScrollPositionListener ---------------------------