3 files changed, 52 insertions, 31 deletions

diff --git a/dom/base/CustomElementRegistry.cpp b/dom/base/CustomElementRegistry.cpp
index 200668f9e..0f03b16bd 100644
--- a/dom/base/CustomElementRegistry.cpp
+++ b/dom/base/CustomElementRegistry.cpp
@@ -138,6 +138,48 @@ CustomElementData::CustomElementData(nsIAtom* aType, State aState)
 {
 }
 
+void
+CustomElementData::SetCustomElementDefinition(CustomElementDefinition* aDefinition)
+{
+  MOZ_ASSERT(mState == State::eCustom);
+  MOZ_ASSERT(!mCustomElementDefinition);
+  MOZ_ASSERT(aDefinition->mType == mType);
+
+  mCustomElementDefinition = aDefinition;
+}
+
+CustomElementDefinition*
+CustomElementData::GetCustomElementDefinition()
+{
+  MOZ_ASSERT(mCustomElementDefinition ? mState == State::eCustom
+                                      : mState != State::eCustom);
+
+  return mCustomElementDefinition;
+}
+
+void
+CustomElementData::Traverse(nsCycleCollectionTraversalCallback& aCb) const
+{
+  for (uint32_t i = 0; i < mReactionQueue.Length(); i++) {
+    if (mReactionQueue[i]) {
+      mReactionQueue[i]->Traverse(aCb);
+    }
+  }
+
+  if (mCustomElementDefinition) {
+    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "mCustomElementDefinition");
+    aCb.NoteNativeChild(mCustomElementDefinition,
+      NS_CYCLE_COLLECTION_PARTICIPANT(CustomElementDefinition));
+  }
+}
+
+void
+CustomElementData::Unlink()
+{
+  mReactionQueue.Clear();
+  mCustomElementDefinition = nullptr;
+}
+
 //-----------------------------------------------------
 // CustomElementRegistry
 
diff --git a/dom/base/CustomElementRegistry.h b/dom/base/CustomElementRegistry.h
index 867c92647..d3dfef682 100644
--- a/dom/base/CustomElementRegistry.h
+++ b/dom/base/CustomElementRegistry.h
@@ -130,24 +130,16 @@ struct CustomElementData
   // e.g., create an element, insert a node.
   AutoTArray<UniquePtr<CustomElementReaction>, 3> mReactionQueue;
 
-  RefPtr<CustomElementDefinition> mCustomElementDefinition;
-
-  void
-  SetCustomElementDefinition(CustomElementDefinition* aDefinition)
-  {
-    MOZ_ASSERT(!mCustomElementDefinition);
-
-    mCustomElementDefinition = aDefinition;
-  }
+  void SetCustomElementDefinition(CustomElementDefinition* aDefinition);
+  CustomElementDefinition* GetCustomElementDefinition();
 
-  CustomElementDefinition*
-  GetCustomElementDefinition()
-  {
-    return mCustomElementDefinition;
-  }
+  void Traverse(nsCycleCollectionTraversalCallback& aCb) const;
+  void Unlink();
 
 private:
   virtual ~CustomElementData() {}
+
+  RefPtr<CustomElementDefinition> mCustomElementDefinition;
 };
 
 #define ALEADY_CONSTRUCTED_MARKER nullptr
@@ -167,7 +159,8 @@ struct CustomElementDefinition
                           mozilla::dom::LifecycleCallbacks* aCallbacks,
                           uint32_t aDocOrder);
 
-  // The type (name) for this custom element.
+  // The type (name) for this custom element, for <button is="x-foo"> or <x-foo>
+  // this would be x-foo.
   nsCOMPtr<nsIAtom> mType;
 
   // The localname to (e.g. <button is=type> -- this would be button).
diff --git a/dom/base/FragmentOrElement.cpp b/dom/base/FragmentOrElement.cpp
index a851190ff..526c3c9d4 100644
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -583,19 +583,7 @@ FragmentOrElement::nsDOMSlots::Traverse(nsCycleCollectionTraversalCallback &cb)
   cb.NoteXPCOMChild(mExtendedSlots->mXBLInsertionParent.get());
 
   if (mExtendedSlots->mCustomElementData) {
-    for (uint32_t i = 0;
-         i < mExtendedSlots->mCustomElementData->mReactionQueue.Length(); i++) {
-      if (mExtendedSlots->mCustomElementData->mReactionQueue[i]) {
-        mExtendedSlots->mCustomElementData->mReactionQueue[i]->Traverse(cb);
-      }
-    }
-
-    if (mExtendedSlots->mCustomElementData->mCustomElementDefinition) {
-      NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb,
-        "mExtendedSlots->mCustomElementData->mCustomElementDefinition");
-      cb.NoteNativeChild(mExtendedSlots->mCustomElementData->mCustomElementDefinition,
-        NS_CYCLE_COLLECTION_PARTICIPANT(CustomElementDefinition));
-    }
+    mExtendedSlots->mCustomElementData->Traverse(cb);
   }
 
   for (auto iter = mExtendedSlots->mRegisteredIntersectionObservers.Iter();
@@ -633,9 +621,7 @@ FragmentOrElement::nsDOMSlots::Unlink()
   MOZ_ASSERT(!(mExtendedSlots->mXBLBinding));
   mExtendedSlots->mXBLInsertionParent = nullptr;
   if (mExtendedSlots->mCustomElementData) {
-    if (mExtendedSlots->mCustomElementData->mCustomElementDefinition) {
-      mExtendedSlots->mCustomElementData->mCustomElementDefinition = nullptr;
-    }
+    mExtendedSlots->mCustomElementData->Unlink();
     mExtendedSlots->mCustomElementData = nullptr;
   }
   mExtendedSlots->mRegisteredIntersectionObservers.Clear();