Test land bug 394442, will back out after tp/tp2/tdhtml results

content/base/src/nsGenericElement.cpp

@@ -2265,6 +2265,10 @@ nsGenericElement::DispatchDOMEvent(nsEvent* aEvent,
 nsIAtom*
 nsGenericElement::GetID() const
 {
+  if (!HasFlag(NODE_MAY_HAVE_ID)) {
+    return nsnull;
+  }
+
   nsIAtom* IDName = GetIDAttributeName();
   if (IDName) {
     const nsAttrValue* attrVal = mAttrsAndChildren.GetAttr(IDName);
@@ -2287,6 +2291,9 @@ nsGenericElement::GetID() const
       }
     }
   }
+
+  nsINode* node = const_cast<nsINode*>(static_cast<const nsINode*>(this));
+  node->UnsetFlags(NODE_MAY_HAVE_ID);
   return nsnull;
 }
 
@@ -3680,6 +3687,7 @@ nsGenericElement::ParseAttribute(PRInt32 aNamespaceID,
 {
   if (aNamespaceID == kNameSpaceID_None &&
       aAttribute == GetIDAttributeName() && !aValue.IsEmpty()) {
+    SetFlags(NODE_MAY_HAVE_ID);
     // Store id as an atom.  id="" means that the element has no id,
     // not that it has an emptystring as the id.
     aResult.ParseAtom(aValue);