Backed out changeset 63cafb0c2f0f (bug 1315837) for causing bug 1317415.

dom/base/DOMIntersectionObserver.cpp

@@ -159,23 +159,15 @@ DOMIntersectionObserver::Observe(Element& aTarget)
 void
 DOMIntersectionObserver::Unobserve(Element& aTarget)
 {
-  if (UnlinkTarget(aTarget)) {
-    aTarget.UnregisterIntersectionObserver(this);
+  if (!mObservationTargets.Contains(&aTarget)) {
+    return;
   }
-}
-
-bool
-DOMIntersectionObserver::UnlinkTarget(Element& aTarget)
-{
-    if (!mObservationTargets.Contains(&aTarget)) {
-        return false;
-    }
-    if (mObservationTargets.Count() == 1) {
-        Disconnect();
-        return false;
-    }
-    mObservationTargets.RemoveEntry(&aTarget);
-    return true;
+  if (mObservationTargets.Count() == 1) {
+    Disconnect();
+    return;
+  }
+  aTarget.UnregisterIntersectionObserver(this);
+  mObservationTargets.RemoveEntry(&aTarget);
 }
 
 void
@@ -200,10 +192,8 @@ DOMIntersectionObserver::Disconnect()
     target->UnregisterIntersectionObserver(this);
   }
   mObservationTargets.Clear();
-  if (mOwner) {
-    nsIDocument* document = mOwner->GetExtantDoc();
-    document->RemoveIntersectionObserver(this);
-  }
+  nsIDocument* document = mOwner->GetExtantDoc();
+  document->RemoveIntersectionObserver(this);
   mConnected = false;
 }
 

dom/base/DOMIntersectionObserver.h

@@ -142,9 +142,7 @@ public:
   void Observe(Element& aTarget);
   void Unobserve(Element& aTarget);
 
-  bool UnlinkTarget(Element& aTarget);
   void Disconnect();
-
   void TakeRecords(nsTArray<RefPtr<DOMIntersectionObserverEntry>>& aRetVal);
 
   mozilla::dom::IntersectionCallback* IntersectionCallback() { return mCallback; }

dom/base/nsNodeUtils.cpp

@@ -297,15 +297,6 @@ nsNodeUtils::LastRelease(nsINode* aNode)
                                          NodeWillBeDestroyed, (aNode));
     }
 
-    if (aNode->IsElement()) {
-      Element* elem = aNode->AsElement();
-      FragmentOrElement::nsDOMSlots* domSlots =
-        static_cast<FragmentOrElement::nsDOMSlots*>(slots);
-      for (auto& reg : domSlots->mRegisteredIntersectionObservers) {
-        reg.observer->UnlinkTarget(*elem);
-      }
-    }
-
     delete slots;
     aNode->mSlots = nullptr;
   }