Bug 1525101 - Make the XULPopupManager caller to GenerateChildFrames sound. r=mats

It only works basically by chance with XBL and doesn't handle any kind of
dynamic insertion. See comment 4 in the bug for the diagnostic.

Differential Revision: https://phabricator.services.mozilla.com/D19489

--HG--
extra : moz-landing-system : lando

layout/xul/nsMenuPopupFrame.cpp

@@ -58,6 +58,7 @@
 
 using namespace mozilla;
 using mozilla::dom::Event;
+using mozilla::dom::Document;
 using mozilla::dom::KeyboardEvent;
 
 int8_t nsMenuPopupFrame::sDefaultLevelIsTop = -1;
@@ -391,15 +392,6 @@ void nsXULPopupShownEvent::CancelListener() {
 NS_IMPL_ISUPPORTS_INHERITED(nsXULPopupShownEvent, Runnable,
                             nsIDOMEventListener);
 
-void nsMenuPopupFrame::SetInitialChildList(ChildListID aListID,
-                                           nsFrameList& aChildList) {
-  // unless the list is empty, indicate that children have been generated.
-  if (aListID == kPrincipalList && aChildList.NotEmpty()) {
-    mGeneratedChildren = true;
-  }
-  nsBoxFrame::SetInitialChildList(aListID, aChildList);
-}
-
 bool nsMenuPopupFrame::IsLeafDynamic() const {
   if (mGeneratedChildren) return false;
 

layout/xul/nsMenuPopupFrame.h

@@ -247,9 +247,6 @@ class nsMenuPopupFrame final : public nsBoxFrame,
   nsresult CreateWidgetForView(nsView* aView);
   uint8_t GetShadowStyle();
 
-  virtual void SetInitialChildList(ChildListID aListID,
-                                   nsFrameList& aChildList) override;
-
   virtual bool IsLeafDynamic() const override;
 
   virtual void UpdateWidgetProperties() override;

layout/xul/nsXULPopupManager.cpp

@@ -1284,8 +1284,11 @@ void nsXULPopupManager::FirePopupShowingEvent(nsIContent* aPopup,
   nsPopupType popupType = popupFrame->PopupType();
 
   // generate the child frames if they have not already been generated
-  if (!popupFrame->HasGeneratedChildren()) {
-    popupFrame->SetGeneratedChildren();
+  const bool generateFrames = popupFrame->IsLeaf();
+  MOZ_ASSERT_IF(generateFrames, !popupFrame->HasGeneratedChildren());
+  popupFrame->SetGeneratedChildren();
+  if (generateFrames) {
+    MOZ_ASSERT(popupFrame->PrincipalChildList().IsEmpty());
     presShell->FrameConstructor()->GenerateChildFrames(popupFrame);
   }