Bug 1096635 - Update XBL insertion parent for dynamic default content. r=mrbkap

dom/xbl/XBLChildrenElement.h

@@ -55,12 +55,20 @@ public:
   {
     mInsertedChildren.AppendElement(aChild);
     aChild->SetXBLInsertionParent(GetParent());
+
+    // Appending an inserted child causes the inserted
+    // children to be projected instead of default content.
+    MaybeRemoveDefaultContent();
   }
 
   void InsertInsertedChildAt(nsIContent* aChild, uint32_t aIndex)
   {
     mInsertedChildren.InsertElementAt(aIndex, aChild);
     aChild->SetXBLInsertionParent(GetParent());
+
+    // Inserting an inserted child causes the inserted
+    // children to be projected instead of default content.
+    MaybeRemoveDefaultContent();
   }
 
   void RemoveInsertedChild(nsIContent* aChild)
@@ -70,6 +78,10 @@ public:
     //NS_ASSERTION(mInsertedChildren.Contains(aChild),
     //             "Removing child that's not there");
     mInsertedChildren.RemoveElement(aChild);
+
+    // After removing the inserted child, default content
+    // may be projected into this insertion point.
+    MaybeSetupDefaultContent();
   }
 
   void ClearInsertedChildren()
@@ -78,6 +90,10 @@ public:
       mInsertedChildren[c]->SetXBLInsertionParent(nullptr);
     }
     mInsertedChildren.Clear();
+
+    // After clearing inserted children, default content
+    // will be projected into this insertion point.
+    MaybeSetupDefaultContent();
   }
 
   void MaybeSetupDefaultContent()

dom/xbl/nsBindingManager.cpp

@@ -884,6 +884,19 @@ nsBindingManager::ContentAppended(nsIDocument* aDocument,
   // Try to find insertion points for all the new kids.
   XBLChildrenElement* point = nullptr;
   nsIContent* parent = aContainer;
+
+  // Handle appending of default content.
+  if (parent && parent->IsActiveChildrenElement()) {
+    XBLChildrenElement* childrenEl = static_cast<XBLChildrenElement*>(parent);
+    if (childrenEl->HasInsertedChildren()) {
+      // Appending default content that isn't being used. Ignore.
+      return;
+    }
+
+    childrenEl->MaybeSetupDefaultContent();
+    parent = childrenEl->GetParent();
+  }
+
   bool first = true;
   do {
     nsXBLBinding* binding = GetBindingWithContent(parent);
@@ -957,6 +970,18 @@ nsBindingManager::ContentRemoved(nsIDocument* aDocument,
 
   XBLChildrenElement* point = nullptr;
   nsIContent* parent = aContainer;
+
+  // Handle appending of default content.
+  if (parent && parent->IsActiveChildrenElement()) {
+    XBLChildrenElement* childrenEl = static_cast<XBLChildrenElement*>(parent);
+    if (childrenEl->HasInsertedChildren()) {
+      // Removing default content that isn't being used. Ignore.
+      return;
+    }
+
+    parent = childrenEl->GetParent();
+  }
+
   do {
     nsXBLBinding* binding = GetBindingWithContent(parent);
     if (!binding) {
@@ -1075,6 +1100,19 @@ nsBindingManager::HandleChildInsertion(nsIContent* aContainer,
 
   XBLChildrenElement* point = nullptr;
   nsIContent* parent = aContainer;
+
+  // Handle insertion of default content.
+  if (parent && parent->IsActiveChildrenElement()) {
+    XBLChildrenElement* childrenEl = static_cast<XBLChildrenElement*>(parent);
+    if (childrenEl->HasInsertedChildren()) {
+      // Inserting default content that isn't being used. Ignore.
+      return;
+    }
+
+    childrenEl->MaybeSetupDefaultContent();
+    parent = childrenEl->GetParent();
+  }
+
   while (parent) {
     nsXBLBinding* binding = GetBindingWithContent(parent);
     if (!binding) {