Merge pull request #998 from MoonchildProductions/master

Merge master into Sync-weave

33 files changed, 233 insertions, 244 deletions

diff --git a/dom/base/Attr.cpp b/dom/base/Attr.cpp
index 6eb3b49fd..71b559392 100644
--- a/dom/base/Attr.cpp
+++ b/dom/base/Attr.cpp
@@ -59,8 +59,6 @@ Attr::Attr(nsDOMAttributeMap *aAttrMap,
 NS_IMPL_CYCLE_COLLECTION_CLASS(Attr)
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Attr)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
-
   if (!nsINode::Traverse(tmp, cb)) {
     return NS_SUCCESS_INTERRUPTED_TRAVERSE;
   }
diff --git a/dom/base/CustomElementRegistry.cpp b/dom/base/CustomElementRegistry.cpp
index 00ee3d42f..3f202d33b 100644
--- a/dom/base/CustomElementRegistry.cpp
+++ b/dom/base/CustomElementRegistry.cpp
@@ -138,7 +138,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(CustomElementRegistry)
   }
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mWhenDefinedPromiseMap)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mWindow)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(CustomElementRegistry)
diff --git a/dom/base/DOMException.cpp b/dom/base/DOMException.cpp
index dfda47316..9fbb2f242 100644
--- a/dom/base/DOMException.cpp
+++ b/dom/base/DOMException.cpp
@@ -165,7 +165,6 @@ NS_IMPL_CYCLE_COLLECTION_CLASS(Exception)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Exception)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mLocation)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mData)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(Exception)
diff --git a/dom/base/DOMIntersectionObserver.cpp b/dom/base/DOMIntersectionObserver.cpp
index e39abf1a6..389b93071 100644
--- a/dom/base/DOMIntersectionObserver.cpp
+++ b/dom/base/DOMIntersectionObserver.cpp
@@ -43,16 +43,17 @@ NS_IMPL_CYCLE_COLLECTION_TRACE_END
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(DOMIntersectionObserver)
   NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+  tmp->Disconnect();
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mOwner)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocument)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mCallback)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mRoot)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mQueuedEntries)
-  tmp->Disconnect();
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(DOMIntersectionObserver)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocument)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCallback)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRoot)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mQueuedEntries)
@@ -153,30 +154,34 @@ DOMIntersectionObserver::Observe(Element& aTarget)
     return;
   }
   aTarget.RegisterIntersectionObserver(this);
-  mObservationTargets.PutEntry(&aTarget);
+  mObservationTargets.AppendElement(&aTarget);
   Connect();
 }
 
 void
 DOMIntersectionObserver::Unobserve(Element& aTarget)
 {
-  if (UnlinkTarget(aTarget)) {
-    aTarget.UnregisterIntersectionObserver(this);
+  if (!mObservationTargets.Contains(&aTarget)) {
+    // You're not on the list, buddy!
+    return;
   }
+  
+  if (mObservationTargets.Length() == 1) {
+    Disconnect();
+    return;
+  }
+
+  mObservationTargets.RemoveElement(&aTarget);
+  aTarget.UnregisterIntersectionObserver(this);
 }
 
-bool
+void
 DOMIntersectionObserver::UnlinkTarget(Element& aTarget)
 {
-    if (!mObservationTargets.Contains(&aTarget)) {
-        return false;
-    }
-    if (mObservationTargets.Count() == 1) {
-        Disconnect();
-        return false;
-    }
-    mObservationTargets.RemoveEntry(&aTarget);
-    return true;
+  mObservationTargets.RemoveElement(&aTarget);
+  if (mObservationTargets.Length() == 0) {
+    Disconnect();
+  }
 }
 
 void
@@ -185,10 +190,11 @@ DOMIntersectionObserver::Connect()
   if (mConnected) {
     return;
   }
+  
   mConnected = true;
-
-  nsIDocument* document = mOwner->GetExtantDoc();
-  document->AddIntersectionObserver(this);
+  if (mDocument) {
+    mDocument->AddIntersectionObserver(this);
+  }
 }
 
 void
@@ -197,18 +203,17 @@ DOMIntersectionObserver::Disconnect()
   if (!mConnected) {
     return;
   }
-  for (auto iter = mObservationTargets.Iter(); !iter.Done(); iter.Next()) {
-    Element* target = iter.Get()->GetKey();
+
+  mConnected = false;
+
+  for (size_t i = 0; i < mObservationTargets.Length(); ++i) {
+    Element* target = mObservationTargets.ElementAt(i);
     target->UnregisterIntersectionObserver(this);
   }
   mObservationTargets.Clear();
-  if (mOwner) {
-    nsIDocument* document = mOwner->GetExtantDoc();
-    if (document) {
-      document->RemoveIntersectionObserver(this);
-    }
+  if (mDocument) {
+    mDocument->RemoveIntersectionObserver(this);
   }
-  mConnected = false;
 }
 
 void
@@ -269,17 +274,21 @@ DOMIntersectionObserver::Update(nsIDocument* aDocument, DOMHighResTimeStamp time
     root = mRoot;
     rootFrame = root->GetPrimaryFrame();
     if (rootFrame) {
+      nsRect rootRectRelativeToRootFrame;
       if (rootFrame->GetType() == nsGkAtoms::scrollFrame) {
+        // rootRectRelativeToRootFrame should be the content rect of rootFrame, not including the scrollbars.
         nsIScrollableFrame* scrollFrame = do_QueryFrame(rootFrame);
-        rootRect = nsLayoutUtils::TransformFrameRectToAncestor(
-          rootFrame,
-          rootFrame->GetContentRectRelativeToSelf(),
-          scrollFrame->GetScrolledFrame());
+        rootRectRelativeToRootFrame = scrollFrame->GetScrollPortRect();
       } else {
-        rootRect = nsLayoutUtils::GetAllInFlowRectsUnion(rootFrame,
-          nsLayoutUtils::GetContainingBlockForClientRect(rootFrame),
-          nsLayoutUtils::RECTS_ACCOUNT_FOR_TRANSFORMS);
+        // rootRectRelativeToRootFrame should be the border rect of rootFrame.
+        rootRectRelativeToRootFrame = rootFrame->GetRectRelativeToSelf();
       }
+      nsIFrame* containingBlock =
+        nsLayoutUtils::GetContainingBlockForClientRect(rootFrame);
+      rootRect =
+        nsLayoutUtils::TransformFrameRectToAncestor(rootFrame,
+                                                    rootRectRelativeToRootFrame,
+                                                    containingBlock);
     }
   } else {
     nsCOMPtr<nsIPresShell> presShell = aDocument->GetShell();
@@ -288,12 +297,25 @@ DOMIntersectionObserver::Update(nsIDocument* aDocument, DOMHighResTimeStamp time
       if (rootFrame) {
         nsPresContext* presContext = rootFrame->PresContext();
         while (!presContext->IsRootContentDocument()) {
-          presContext = rootFrame->PresContext()->GetParentPresContext();
-          rootFrame = presContext->PresShell()->GetRootScrollFrame();
+          // Walk up the tree
+          presContext = presContext->GetParentPresContext();
+          if (!presContext) {
+            break;
+          }
+          nsIFrame* rootScrollFrame = presContext->PresShell()->GetRootScrollFrame();
+          if (rootScrollFrame) {
+            rootFrame = rootScrollFrame;
+          } else {
+            break;
+          }
         }
         root = rootFrame->GetContent()->AsElement();
         nsIScrollableFrame* scrollFrame = do_QueryFrame(rootFrame);
-        rootRect = scrollFrame->GetScrollPortRect();
+        // If we end up with a null root frame for some reason, we'll proceed
+        // with an empty root intersection rect.
+        if (scrollFrame) {
+          rootRect = scrollFrame->GetScrollPortRect();
+        }
       }
     }
   }
@@ -314,11 +336,12 @@ DOMIntersectionObserver::Update(nsIDocument* aDocument, DOMHighResTimeStamp time
     rootMargin.Side(side) = nsLayoutUtils::ComputeCBDependentValue(basis, coord);
   }
 
-  for (auto iter = mObservationTargets.Iter(); !iter.Done(); iter.Next()) {
-    Element* target = iter.Get()->GetKey();
+  for (size_t i = 0; i < mObservationTargets.Length(); ++i) {
+    Element* target = mObservationTargets.ElementAt(i);
     nsIFrame* targetFrame = target->GetPrimaryFrame();
     nsRect targetRect;
     Maybe<nsRect> intersectionRect;
+    bool isSameDoc = root && root->GetComposedDoc() == target->GetComposedDoc();
 
     if (rootFrame && targetFrame) {
       // If mRoot is set we are testing intersection with a container element
@@ -327,7 +350,7 @@ DOMIntersectionObserver::Update(nsIDocument* aDocument, DOMHighResTimeStamp time
         // Skip further processing of this target if it is not in the same
         // Document as the intersection root, e.g. if root is an element of
         // the main document and target an element from an embedded iframe.
-        if (target->GetComposedDoc() != root->GetComposedDoc()) {
+        if (!isSameDoc) {
           continue;
         }
         // Skip further processing of this target if is not a descendant of the
@@ -344,7 +367,7 @@ DOMIntersectionObserver::Update(nsIDocument* aDocument, DOMHighResTimeStamp time
         nsLayoutUtils::GetContainingBlockForClientRect(targetFrame),
         nsLayoutUtils::RECTS_ACCOUNT_FOR_TRANSFORMS
       );
-      intersectionRect = Some(targetFrame->GetVisualOverflowRect());
+      intersectionRect = Some(targetFrame->GetRectRelativeToSelf());
 
       nsIFrame* containerFrame = nsLayoutUtils::GetCrossDocParentFrame(targetFrame);
       while (containerFrame && containerFrame != rootFrame) {
@@ -399,29 +422,37 @@ DOMIntersectionObserver::Update(nsIDocument* aDocument, DOMHighResTimeStamp time
         intersectionRectRelativeToRoot,
         rootIntersectionRect
       );
-      if (intersectionRect.isSome()) {
-        intersectionRect = Some(nsLayoutUtils::TransformFrameRectToAncestor(
-          nsLayoutUtils::GetContainingBlockForClientRect(rootFrame),
-          intersectionRect.value(),
-          targetFrame->PresContext()->PresShell()->GetRootScrollFrame()
-        ));
+      if (intersectionRect.isSome() && !isSameDoc) {
+        nsRect rect = intersectionRect.value();
+        nsPresContext* presContext = targetFrame->PresContext();
+        nsLayoutUtils::TransformRect(rootFrame,
+          presContext->PresShell()->GetRootScrollFrame(), rect);
+        intersectionRect = Some(rect);
       }
     }
 
-    double targetArea = targetRect.width * targetRect.height;
-    double intersectionArea = !intersectionRect ?
-      0 : intersectionRect->width * intersectionRect->height;
-    double intersectionRatio = targetArea > 0.0 ? intersectionArea / targetArea : 0.0;
+    int64_t targetArea =
+      (int64_t) targetRect.Width() * (int64_t) targetRect.Height();
+    int64_t intersectionArea = !intersectionRect ? 0 :
+      (int64_t) intersectionRect->Width() *
+      (int64_t) intersectionRect->Height();
+    
+    double intersectionRatio;
+    if (targetArea > 0.0) {
+      intersectionRatio = (double) intersectionArea / (double) targetArea;
+    } else {
+      intersectionRatio = intersectionRect.isSome() ? 1.0 : 0.0;
+    }
 
-    size_t threshold = -1;
+    int32_t threshold = -1;
     if (intersectionRatio > 0.0) {
       if (intersectionRatio >= 1.0) {
         intersectionRatio = 1.0;
-        threshold = mThresholds.Length();
+        threshold = (int32_t)mThresholds.Length();
       } else {
         for (size_t k = 0; k < mThresholds.Length(); ++k) {
           if (mThresholds[k] <= intersectionRatio) {
-            threshold = k + 1;
+            threshold = (int32_t)k + 1;
           } else {
             break;
           }
@@ -468,6 +499,7 @@ DOMIntersectionObserver::QueueIntersectionObserverEntry(Element* aTarget,
     rootBounds.forget(),
     boundingClientRect.forget(),
     intersectionRect.forget(),
+    aIntersectionRect.isSome(),
     aTarget, aIntersectionRatio);
   mQueuedEntries.AppendElement(entry.forget());
 }
@@ -480,7 +512,7 @@ DOMIntersectionObserver::Notify()
   }
   mozilla::dom::Sequence<mozilla::OwningNonNull<DOMIntersectionObserverEntry>> entries;
   if (entries.SetCapacity(mQueuedEntries.Length(), mozilla::fallible)) {
-    for (uint32_t i = 0; i < mQueuedEntries.Length(); ++i) {
+    for (size_t i = 0; i < mQueuedEntries.Length(); ++i) {
       RefPtr<DOMIntersectionObserverEntry> next = mQueuedEntries[i];
       *entries.AppendElement(mozilla::fallible) = next;
     }
diff --git a/dom/base/DOMIntersectionObserver.h b/dom/base/DOMIntersectionObserver.h
index 8144fc5c5..8674fe25d 100644
--- a/dom/base/DOMIntersectionObserver.h
+++ b/dom/base/DOMIntersectionObserver.h
@@ -30,6 +30,7 @@ public:
                                RefPtr<DOMRect> aRootBounds,
                                RefPtr<DOMRect> aBoundingClientRect,
                                RefPtr<DOMRect> aIntersectionRect,
+                               bool aIsIntersecting,
                                Element* aTarget,
                                double aIntersectionRatio)
   : mOwner(aOwner),
@@ -37,6 +38,7 @@ public:
     mRootBounds(aRootBounds),
     mBoundingClientRect(aBoundingClientRect),
     mIntersectionRect(aIntersectionRect),
+    mIsIntersecting(aIsIntersecting),
     mTarget(aTarget),
     mIntersectionRatio(aIntersectionRatio)
   {
@@ -74,6 +76,11 @@ public:
     return mIntersectionRect;
   }
 
+  bool IsIntersecting()
+  {
+    return mIsIntersecting;
+  }
+
   double IntersectionRatio()
   {
     return mIntersectionRatio;
@@ -90,6 +97,7 @@ protected:
   RefPtr<DOMRect>       mRootBounds;
   RefPtr<DOMRect>       mBoundingClientRect;
   RefPtr<DOMRect>       mIntersectionRect;
+  bool                  mIsIntersecting;
   RefPtr<Element>       mTarget;
   double                mIntersectionRatio;
 };
@@ -101,12 +109,17 @@ protected:
 class DOMIntersectionObserver final : public nsISupports,
                                       public nsWrapperCache
 {
-  virtual ~DOMIntersectionObserver() { }
+  virtual ~DOMIntersectionObserver() {
+    Disconnect();
+  }
 
 public:
   DOMIntersectionObserver(already_AddRefed<nsPIDOMWindowInner>&& aOwner,
                           mozilla::dom::IntersectionCallback& aCb)
-  : mOwner(aOwner), mCallback(&aCb), mConnected(false)
+  : mOwner(aOwner)
+  , mDocument(mOwner->GetExtantDoc())
+  , mCallback(&aCb)
+  , mConnected(false)
   {
   }
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
@@ -142,7 +155,7 @@ public:
   void Observe(Element& aTarget);
   void Unobserve(Element& aTarget);
 
-  bool UnlinkTarget(Element& aTarget);
+  void UnlinkTarget(Element& aTarget);
   void Disconnect();
 
   void TakeRecords(nsTArray<RefPtr<DOMIntersectionObserverEntry>>& aRetVal);
@@ -164,11 +177,15 @@ protected:
                                       double aIntersectionRatio);
 
   nsCOMPtr<nsPIDOMWindowInner>                    mOwner;
+  RefPtr<nsIDocument>                             mDocument;
   RefPtr<mozilla::dom::IntersectionCallback>      mCallback;
   RefPtr<Element>                                 mRoot;
   nsCSSRect                                       mRootMargin;
   nsTArray<double>                                mThresholds;
-  nsTHashtable<nsPtrHashKey<Element>>             mObservationTargets;
+  
+  // Holds raw pointers which are explicitly cleared by UnlinkTarget().
+  nsTArray<Element*>                              mObservationTargets;
+  
   nsTArray<RefPtr<DOMIntersectionObserverEntry>>  mQueuedEntries;
   bool                                            mConnected;
 };
diff --git a/dom/base/Element.cpp b/dom/base/Element.cpp
index 3760dc43f..5c3277e84 100644
--- a/dom/base/Element.cpp
+++ b/dom/base/Element.cpp
@@ -687,19 +687,23 @@ Element::GetScrollFrame(nsIFrame **aStyledFrame, bool aFlushLayout)
 }
 
 void
-Element::ScrollIntoView()
+Element::ScrollIntoView(const BooleanOrScrollIntoViewOptions& aObject)
 {
-  ScrollIntoView(ScrollIntoViewOptions());
-}
+  if (aObject.IsScrollIntoViewOptions()) {
+    return ScrollIntoView(aObject.GetAsScrollIntoViewOptions());
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(aObject.IsBoolean());
 
-void
-Element::ScrollIntoView(bool aTop)
-{
   ScrollIntoViewOptions options;
-  if (!aTop) {
+  if (aObject.GetAsBoolean()) {
+    options.mBlock = ScrollLogicalPosition::Start;
+    options.mInline = ScrollLogicalPosition::Nearest;
+  } else {
     options.mBlock = ScrollLogicalPosition::End;
+    options.mInline = ScrollLogicalPosition::Nearest;
   }
-  ScrollIntoView(options);
+  return ScrollIntoView(options);
 }
 
 void
@@ -716,9 +720,41 @@ Element::ScrollIntoView(const ScrollIntoViewOptions &aOptions)
     return;
   }
 
-  int16_t vpercent = (aOptions.mBlock == ScrollLogicalPosition::Start)
-                       ? nsIPresShell::SCROLL_TOP
-                       : nsIPresShell::SCROLL_BOTTOM;
+  int16_t vpercent = nsIPresShell::SCROLL_CENTER;
+  switch (aOptions.mBlock) {
+    case ScrollLogicalPosition::Start:
+      vpercent = nsIPresShell::SCROLL_TOP;
+      break;
+    case ScrollLogicalPosition::Center:
+      vpercent = nsIPresShell::SCROLL_CENTER;
+      break;
+    case ScrollLogicalPosition::End:
+      vpercent = nsIPresShell::SCROLL_BOTTOM;
+      break;
+    case ScrollLogicalPosition::Nearest:
+      vpercent = nsIPresShell::SCROLL_MINIMUM;
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unexpected ScrollLogicalPosition value");
+  }
+
+  int16_t hpercent = nsIPresShell::SCROLL_CENTER;
+  switch (aOptions.mInline) {
+    case ScrollLogicalPosition::Start:
+      hpercent = nsIPresShell::SCROLL_LEFT;
+      break;
+    case ScrollLogicalPosition::Center:
+      hpercent = nsIPresShell::SCROLL_CENTER;
+      break;
+    case ScrollLogicalPosition::End:
+      hpercent = nsIPresShell::SCROLL_RIGHT;
+      break;
+    case ScrollLogicalPosition::Nearest:
+      hpercent = nsIPresShell::SCROLL_MINIMUM;
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unexpected ScrollLogicalPosition value");
+  }
 
   uint32_t flags = nsIPresShell::SCROLL_OVERFLOW_HIDDEN;
   if (aOptions.mBehavior == ScrollBehavior::Smooth) {
@@ -731,7 +767,9 @@ Element::ScrollIntoView(const ScrollIntoViewOptions &aOptions)
                                    nsIPresShell::ScrollAxis(
                                      vpercent,
                                      nsIPresShell::SCROLL_ALWAYS),
-                                   nsIPresShell::ScrollAxis(),
+                                   nsIPresShell::ScrollAxis(
+                                     hpercent,
+                                     nsIPresShell::SCROLL_ALWAYS),
                                    flags);
 }
 
@@ -3947,7 +3985,7 @@ Element::ClearDataset()
   slots->mDataset = nullptr;
 }
 
-nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>*
+nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>*
 Element::RegisteredIntersectionObservers()
 {
   nsDOMSlots* slots = DOMSlots();
@@ -3962,7 +4000,7 @@ enum nsPreviousIntersectionThreshold {
 void
 Element::RegisterIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
+  nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
     RegisteredIntersectionObservers();
   if (observers->Contains(aObserver)) {
     return;
@@ -3979,7 +4017,7 @@ Element::RegisterIntersectionObserver(DOMIntersectionObserver* aObserver)
 void
 Element::UnregisterIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
+  nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
     RegisteredIntersectionObservers();
   observers->Remove(aObserver);
 }
@@ -3987,7 +4025,7 @@ Element::UnregisterIntersectionObserver(DOMIntersectionObserver* aObserver)
 bool
 Element::UpdateIntersectionObservation(DOMIntersectionObserver* aObserver, int32_t aThreshold)
 {
-  nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
+  nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
     RegisteredIntersectionObservers();
   if (!observers->Contains(aObserver)) {
     return false;
diff --git a/dom/base/Element.h b/dom/base/Element.h
index c269ab14a..ce84b74fb 100644
--- a/dom/base/Element.h
+++ b/dom/base/Element.h
@@ -818,9 +818,10 @@ public:
     return slots ? slots->mShadowRoot.get() : nullptr;
   }
 
-  void ScrollIntoView();
-  void ScrollIntoView(bool aTop);
+private:
   void ScrollIntoView(const ScrollIntoViewOptions &aOptions);
+public:
+  void ScrollIntoView(const BooleanOrScrollIntoViewOptions& aObject);
   void Scroll(double aXScroll, double aYScroll);
   void Scroll(const ScrollToOptions& aOptions);
   void ScrollTo(double aXScroll, double aYScroll);
@@ -1382,7 +1383,8 @@ protected:
   nsDOMTokenList* GetTokenList(nsIAtom* aAtom,
                                const DOMTokenListSupportedTokenArray aSupportedTokens = nullptr);
 
-  nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>* RegisteredIntersectionObservers();
+  nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>* 
+    RegisteredIntersectionObservers();
 
 private:
   /**
diff --git a/dom/base/File.cpp b/dom/base/File.cpp
index 7d86dfe8a..1d5ab73e7 100755
--- a/dom/base/File.cpp
+++ b/dom/base/File.cpp
@@ -138,7 +138,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Blob)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mParent)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(Blob)
diff --git a/dom/base/FormData.cpp b/dom/base/FormData.cpp
index 6095286be..52bdd9210 100644
--- a/dom/base/FormData.cpp
+++ b/dom/base/FormData.cpp
@@ -84,7 +84,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(FormData)
                                 "mFormData[i].GetAsBlob()", 0);
   }
 
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(FormData)
diff --git a/dom/base/FragmentOrElement.cpp b/dom/base/FragmentOrElement.cpp
index fde983e7c..9106778df 100644
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -585,6 +585,12 @@ FragmentOrElement::nsDOMSlots::Traverse(nsCycleCollectionTraversalCallback &cb,
       mCustomElementData->mCallbackQueue[i]->Traverse(cb);
     }
   }
+
+  for (auto iter = mRegisteredIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+    DOMIntersectionObserver* observer = iter.Key();
+    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mSlots->mRegisteredIntersectionObservers[i]");
+    cb.NoteXPCOMChild(observer);
+  }
 }
 
 void
@@ -1872,10 +1878,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(FragmentOrElement)
     NS_IMPL_CYCLE_COLLECTION_DESCRIBE(FragmentOrElement, tmp->mRefCnt.get())
   }
 
-  // Always need to traverse script objects, so do that before we check
-  // if we're uncollectable.
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
-
   if (!nsINode::Traverse(tmp, cb)) {
     return NS_SUCCESS_INTERRUPTED_TRAVERSE;
   }
diff --git a/dom/base/FragmentOrElement.h b/dom/base/FragmentOrElement.h
index 7c74e9cd4..f0cc29f22 100644
--- a/dom/base/FragmentOrElement.h
+++ b/dom/base/FragmentOrElement.h
@@ -354,7 +354,8 @@ public:
     /**
      * Registered Intersection Observers on the element.
      */
-    nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t> mRegisteredIntersectionObservers;
+    nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t> 
+      mRegisteredIntersectionObservers;
   };
 
 protected:
diff --git a/dom/base/Location.cpp b/dom/base/Location.cpp
index e312cffe0..1483c32f9 100644
--- a/dom/base/Location.cpp
+++ b/dom/base/Location.cpp
@@ -80,7 +80,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Location)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mInnerWindow)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(Location)
@@ -790,10 +789,6 @@ Location::GetSearch(nsAString& aSearch)
 NS_IMETHODIMP
 Location::SetSearch(const nsAString& aSearch)
 {
-  if (aSearch.IsEmpty()) {
-    return NS_OK; // Ignore empty string
-  }
-
   nsresult rv = SetSearchInternal(aSearch);
   if (NS_FAILED(rv)) {
     return rv;
diff --git a/dom/base/Navigator.cpp b/dom/base/Navigator.cpp
index 286cd0e79..fdf151b6c 100644
--- a/dom/base/Navigator.cpp
+++ b/dom/base/Navigator.cpp
@@ -223,7 +223,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Navigator)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGamepadServiceTest)
 #endif
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mVRGetDisplaysPromises)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(Navigator)
diff --git a/dom/base/Pose.cpp b/dom/base/Pose.cpp
index 1eab4c173..5bc4ca6de 100644
--- a/dom/base/Pose.cpp
+++ b/dom/base/Pose.cpp
@@ -26,7 +26,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Pose)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mParent)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(Pose)
diff --git a/dom/base/ProcessGlobal.cpp b/dom/base/ProcessGlobal.cpp
index 641f49f98..6cd29ab7c 100644
--- a/dom/base/ProcessGlobal.cpp
+++ b/dom/base/ProcessGlobal.cpp
@@ -52,7 +52,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(ProcessGlobal)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMessageManager)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGlobal)
   tmp->TraverseHostObjectURIs(cb);
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(ProcessGlobal)
diff --git a/dom/base/nsContentList.cpp b/dom/base/nsContentList.cpp
index 43e65777d..c98859ee3 100644
--- a/dom/base/nsContentList.cpp
+++ b/dom/base/nsContentList.cpp
@@ -54,7 +54,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsBaseContentList)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsBaseContentList)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mElements)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(nsBaseContentList)
 
diff --git a/dom/base/nsDOMAttributeMap.cpp b/dom/base/nsDOMAttributeMap.cpp
index 381f267cd..2a90df7e4 100644
--- a/dom/base/nsDOMAttributeMap.cpp
+++ b/dom/base/nsDOMAttributeMap.cpp
@@ -65,7 +65,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsDOMAttributeMap)
   for (auto iter = tmp->mAttributeCache.Iter(); !iter.Done(); iter.Next()) {
     cb.NoteXPCOMChild(static_cast<nsINode*>(iter.Data().get()));
   }
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mContent)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
diff --git a/dom/base/nsDOMMutationObserver.cpp b/dom/base/nsDOMMutationObserver.cpp
index 024ce5e2e..858a30ce5 100644
--- a/dom/base/nsDOMMutationObserver.cpp
+++ b/dom/base/nsDOMMutationObserver.cpp
@@ -506,7 +506,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsDOMMutationObserver)
   NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsDOMMutationObserver)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mReceivers)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mFirstPendingMutation)
diff --git a/dom/base/nsDOMWindowUtils.cpp b/dom/base/nsDOMWindowUtils.cpp
index 291df5f27..2ab5937ac 100644
--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -4033,8 +4033,6 @@ nsDOMWindowUtils::ForceUseCounterFlush(nsIDOMNode *aNode)
   if (nsCOMPtr<nsIDocument> doc = do_QueryInterface(aNode)) {
     mozilla::css::ImageLoader* loader = doc->StyleImageLoader();
     loader->FlushUseCounters();
-
-    static_cast<nsDocument*>(doc.get())->ReportUseCounters();
     return NS_OK;
   }
 
diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index ac9601caf..a6ed419df 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -1395,63 +1395,6 @@ nsDocument::~nsDocument()
 
   NS_ASSERTION(!mIsShowing, "Destroying a currently-showing document");
 
-  if (IsTopLevelContentDocument()) {
-    //don't report for about: pages
-    if (!IsAboutPage()) {
-      // Record the page load
-      uint32_t pageLoaded = 1;
-      Accumulate(Telemetry::MIXED_CONTENT_UNBLOCK_COUNTER, pageLoaded);
-      // Record the mixed content status of the docshell in Telemetry
-      enum {
-        NO_MIXED_CONTENT = 0, // There is no Mixed Content on the page
-        MIXED_DISPLAY_CONTENT = 1, // The page attempted to load Mixed Display Content
-        MIXED_ACTIVE_CONTENT = 2, // The page attempted to load Mixed Active Content
-        MIXED_DISPLAY_AND_ACTIVE_CONTENT = 3 // The page attempted to load Mixed Display & Mixed Active Content
-      };
-
-      bool mixedActiveLoaded = GetHasMixedActiveContentLoaded();
-      bool mixedActiveBlocked = GetHasMixedActiveContentBlocked();
-
-      bool mixedDisplayLoaded = GetHasMixedDisplayContentLoaded();
-      bool mixedDisplayBlocked = GetHasMixedDisplayContentBlocked();
-
-      bool hasMixedDisplay = (mixedDisplayBlocked || mixedDisplayLoaded);
-      bool hasMixedActive = (mixedActiveBlocked || mixedActiveLoaded);
-
-      uint32_t mixedContentLevel = NO_MIXED_CONTENT;
-      if (hasMixedDisplay && hasMixedActive) {
-        mixedContentLevel = MIXED_DISPLAY_AND_ACTIVE_CONTENT;
-      } else if (hasMixedActive){
-        mixedContentLevel = MIXED_ACTIVE_CONTENT;
-      } else if (hasMixedDisplay) {
-        mixedContentLevel = MIXED_DISPLAY_CONTENT;
-      }
-      Accumulate(Telemetry::MIXED_CONTENT_PAGE_LOAD, mixedContentLevel);
-
-      // record mixed object subrequest telemetry
-      if (mHasMixedContentObjectSubrequest) {
-        /* mixed object subrequest loaded on page*/
-        Accumulate(Telemetry::MIXED_CONTENT_OBJECT_SUBREQUEST, 1);
-      } else {
-        /* no mixed object subrequests loaded on page*/
-        Accumulate(Telemetry::MIXED_CONTENT_OBJECT_SUBREQUEST, 0);
-      }
-
-      // record CSP telemetry on this document
-      if (mHasCSP) {
-        Accumulate(Telemetry::CSP_DOCUMENTS_COUNT, 1);
-      }
-      if (mHasUnsafeInlineCSP) {
-        Accumulate(Telemetry::CSP_UNSAFE_INLINE_DOCUMENTS_COUNT, 1);
-      }
-      if (mHasUnsafeEvalCSP) {
-        Accumulate(Telemetry::CSP_UNSAFE_EVAL_DOCUMENTS_COUNT, 1);
-      }
-    }
-  }
-
-  ReportUseCounters();
-
   mInDestructor = true;
   mInUnlinkOrDeletion = true;
 
@@ -1647,10 +1590,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsDocument)
     NS_IMPL_CYCLE_COLLECTION_DESCRIBE(nsDocument, tmp->mRefCnt.get())
   }
 
-  // Always need to traverse script objects, so do that before we check
-  // if we're uncollectable.
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
-
   if (!nsINode::Traverse(tmp, cb)) {
     return NS_SUCCESS_INTERRUPTED_TRAVERSE;
   }
@@ -1736,8 +1675,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsDocument)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOnDemandBuiltInUASheets)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPreloadingImages)
 
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mIntersectionObservers)
-
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSubImportLinks)
 
   for (uint32_t i = 0; i < tmp->mFrameRequestCallbacks.Length(); ++i) {
@@ -12355,40 +12292,27 @@ nsIDocument::InlineScriptAllowedByCSP()
   return allowsInlineScript;
 }
 
-static bool
-MightBeAboutOrChromeScheme(nsIURI* aURI)
-{
-  MOZ_ASSERT(aURI);
-  bool isAbout = true;
-  bool isChrome = true;
-  aURI->SchemeIs("about", &isAbout);
-  aURI->SchemeIs("chrome", &isChrome);
-  return isAbout || isChrome;
-}
-
-void
-nsDocument::ReportUseCounters()
-{
-/* STUB */
-}
-
 void
 nsDocument::AddIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  NS_ASSERTION(mIntersectionObservers.IndexOf(aObserver) == nsTArray<int>::NoIndex,
-               "Intersection observer already in the list");
-  mIntersectionObservers.AppendElement(aObserver);
+  MOZ_ASSERT(!mIntersectionObservers.Contains(aObserver),
+             "Intersection observer already in the list");
+  mIntersectionObservers.PutEntry(aObserver);
 }
 
 void
 nsDocument::RemoveIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  mIntersectionObservers.RemoveElement(aObserver);
+  mIntersectionObservers.RemoveEntry(aObserver);
 }
 
 void
 nsDocument::UpdateIntersectionObservations()
 {
+  if (mIntersectionObservers.IsEmpty()) {
+    return;
+  }
+
   DOMHighResTimeStamp time = 0;
   if (nsPIDOMWindowInner* window = GetInnerWindow()) {
     Performance* perf = window->GetPerformance();
@@ -12396,25 +12320,42 @@ nsDocument::UpdateIntersectionObservations()
       time = perf->Now();
     }
   }
-  for (const auto& observer : mIntersectionObservers) {
-    observer->Update(this, time);
+  nsTArray<RefPtr<DOMIntersectionObserver>> observers(mIntersectionObservers.Count());
+  for (auto iter = mIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+    DOMIntersectionObserver* observer = iter.Get()->GetKey();
+    observers.AppendElement(observer);
+  }
+  for (const auto& observer : observers) {
+    if (observer) {
+      observer->Update(this, time);
+    }
   }
 }
 
 void
 nsDocument::ScheduleIntersectionObserverNotification()
 {
+  if (mIntersectionObservers.IsEmpty()) {
+    return;
+  }
+
   nsCOMPtr<nsIRunnable> notification = NewRunnableMethod(this,
     &nsDocument::NotifyIntersectionObservers);
-  NS_DispatchToCurrentThread(notification);
+  NS_DispatchToCurrentThread(notification.forget());
 }
 
 void
 nsDocument::NotifyIntersectionObservers()
 {
-  nsTArray<RefPtr<DOMIntersectionObserver>> observers(mIntersectionObservers);
+  nsTArray<RefPtr<DOMIntersectionObserver>> observers(mIntersectionObservers.Count());
+  for (auto iter = mIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+    DOMIntersectionObserver* observer = iter.Get()->GetKey();
+    observers.AppendElement(observer);
+  }
   for (const auto& observer : observers) {
-    observer->Notify();
+    if (observer) {
+      observer->Notify();
+    }
   }
 }
 
diff --git a/dom/base/nsDocument.h b/dom/base/nsDocument.h
index 3725b3c18..95fd57545 100644
--- a/dom/base/nsDocument.h
+++ b/dom/base/nsDocument.h
@@ -774,8 +774,6 @@ public:
 
   virtual nsViewportInfo GetViewportInfo(const mozilla::ScreenIntSize& aDisplaySize) override;
 
-  void ReportUseCounters();
-
   virtual void AddIntersectionObserver(
     mozilla::dom::DOMIntersectionObserver* aObserver) override;
   virtual void RemoveIntersectionObserver(
@@ -1341,8 +1339,9 @@ protected:
   // Array of observers
   nsTObserverArray<nsIDocumentObserver*> mObservers;
 
-  // Array of intersection observers
-  nsTArray<RefPtr<mozilla::dom::DOMIntersectionObserver>> mIntersectionObservers;
+  // Hashtable of intersection observers
+  nsTHashtable<nsPtrHashKey<mozilla::dom::DOMIntersectionObserver>>
+    mIntersectionObservers;
 
   // Tracker for animations that are waiting to start.
   // nullptr until GetOrCreatePendingAnimationTracker is called.
@@ -1448,14 +1447,6 @@ public:
   // 'style-sheet-applicable-state-changed' notification.
   bool mSSApplicableStateNotificationPending:1;
 
-  // Whether we have reported use counters for this document with Telemetry yet.
-  // Normally this is only done at document destruction time, but for image
-  // documents (SVG documents) that are not guaranteed to be destroyed, we
-  // report use counters when the image cache no longer has any imgRequestProxys
-  // pointing to them.  We track whether we ever reported use counters so
-  // that we only report them once for the document.
-  bool mReportedUseCounters:1;
-
   // Whether we have filled our pres shell's style set with the document's
   // additional sheets and sheets from the nsStyleSheetService.
   bool mStyleSetFilled:1;
diff --git a/dom/base/nsFrameMessageManager.cpp b/dom/base/nsFrameMessageManager.cpp
index f173678b7..bba4232aa 100644
--- a/dom/base/nsFrameMessageManager.cpp
+++ b/dom/base/nsFrameMessageManager.cpp
@@ -132,7 +132,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsFrameMessageManager)
   }
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mChildManagers)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mParentManager)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(nsFrameMessageManager)
@@ -706,12 +705,6 @@ nsFrameMessageManager::SendRpcMessage(const nsAString& aMessageName,
 static bool
 AllowMessage(size_t aDataLength, const nsAString& aMessageName)
 {
-  static const size_t kMinTelemetryMessageSize = 8192;
-
-  if (aDataLength < kMinTelemetryMessageSize) {
-    return true;
-  }
-
   NS_ConvertUTF16toUTF8 messageName(aMessageName);
   messageName.StripChars("0123456789");
 
diff --git a/dom/base/nsGenericDOMDataNode.cpp b/dom/base/nsGenericDOMDataNode.cpp
index 9688588e0..0ae15e09e 100644
--- a/dom/base/nsGenericDOMDataNode.cpp
+++ b/dom/base/nsGenericDOMDataNode.cpp
@@ -98,10 +98,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsGenericDOMDataNode)
     NS_IMPL_CYCLE_COLLECTION_DESCRIBE(nsGenericDOMDataNode, tmp->mRefCnt.get())
   }
 
-  // Always need to traverse script objects, so do that before we check
-  // if we're uncollectable.
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
-
   if (!nsINode::Traverse(tmp, cb)) {
     return NS_SUCCESS_INTERRUPTED_TRAVERSE;
   }
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 677e1a0ea..ac85e34c0 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -288,7 +288,6 @@ static bool                 gMouseDown                 = false;
 static bool                 gDragServiceDisabled       = false;
 static FILE                *gDumpFile                  = nullptr;
 static uint32_t             gSerialCounter             = 0;
-static TimeStamp            gLastRecordedRecentTimeouts;
 #define STATISTICS_INTERVAL (30 * PR_MSEC_PER_SEC)
 
 #ifdef DEBUG_jst
@@ -1518,7 +1517,6 @@ nsGlobalWindow::nsGlobalWindow(nsGlobalWindow *aOuterWindow)
     mIsPopupSpam(false),
     mBlockScriptedClosingFlag(false),
     mWasOffline(false),
-    mHasHadSlowScript(false),
     mNotifyIdleObserversIdleOnThaw(false),
     mNotifyIdleObserversActiveOnThaw(false),
     mCreatingInnerWindow(false),
@@ -2286,7 +2284,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsGlobalWindow)
 
   tmp->TraverseHostObjectURIs(cb);
 
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsGlobalWindow)
@@ -11542,8 +11539,6 @@ nsGlobalWindow::ShowSlowScriptDialog()
   unsigned lineno;
   bool hasFrame = JS::DescribeScriptedCaller(cx, &filename, &lineno);
 
-  mHasHadSlowScript = true;
-
   if (XRE_IsContentProcess() &&
       ProcessHangMonitor::Get()) {
     ProcessHangMonitor::SlowScriptAction action;
@@ -13399,13 +13394,6 @@ nsGlobalWindow::RunTimeout(Timeout* aTimeout)
     return;
   }
 
-  // Record telemetry information about timers set recently.
-  TimeDuration recordingInterval = TimeDuration::FromMilliseconds(STATISTICS_INTERVAL);
-  if (gLastRecordedRecentTimeouts.IsNull() ||
-      now - gLastRecordedRecentTimeouts > recordingInterval) {
-    gLastRecordedRecentTimeouts = now;
-  }
-
   // Insert a dummy timeout into the list of timeouts between the
   // portion of the list that we are about to process now and those
   // timeouts that will be processed in a future call to
diff --git a/dom/base/nsGlobalWindow.h b/dom/base/nsGlobalWindow.h
index 1cb825a77..1f420895c 100644
--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -1780,11 +1780,6 @@ protected:
   // Window offline status. Checked to see if we need to fire offline event
   bool                          mWasOffline : 1;
 
-  // Represents whether the inner window's page has had a slow script notice.
-  // Only used by inner windows; will always be false for outer windows.
-  // This is used to implement Telemetry measures such as SLOW_SCRIPT_PAGE_COUNT.
-  bool                          mHasHadSlowScript : 1;
-
   // Track what sorts of events we need to fire when thawed
   bool                          mNotifyIdleObserversIdleOnThaw : 1;
   bool                          mNotifyIdleObserversActiveOnThaw : 1;
diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index 4a984d294..dfd380fc2 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -625,7 +625,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsJSContext)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsJSContext)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGlobalObjectRef)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsJSContext)
@@ -1356,9 +1355,20 @@ nsJSContext::RunCycleCollectorSlice()
       TimeStamp now = TimeStamp::Now();
 
       // Only run a limited slice if we're within the max running time.
-      if (TimeBetween(gCCStats.mBeginTime, now) < kMaxICCDuration) {
-        float sliceMultiplier = std::max(TimeBetween(gCCStats.mEndSliceTime, now) / (float)kICCIntersliceDelay, 1.0f);
-        budget = js::SliceBudget(js::TimeBudget(kICCSliceBudget * sliceMultiplier));
+      uint32_t runningTime = TimeBetween(gCCStats.mBeginTime, now);
+      if (runningTime < kMaxICCDuration) {
+        // Try to make up for a delay in running this slice.
+        float sliceDelayMultiplier = TimeBetween(gCCStats.mEndSliceTime, now) / (float)kICCIntersliceDelay;
+        float delaySliceBudget = kICCSliceBudget * sliceDelayMultiplier;
+
+        // Increase slice budgets up to |maxLaterSlice| as we approach
+        // half way through the ICC, to avoid large sync CCs.
+        float percentToHalfDone = std::min(2.0f * runningTime / kMaxICCDuration, 1.0f);
+        const float maxLaterSlice = 40.0f;
+        float laterSliceBudget = maxLaterSlice * percentToHalfDone;
+
+        budget = js::SliceBudget(js::TimeBudget(std::max({delaySliceBudget,
+                  laterSliceBudget, (float)kICCSliceBudget})));
       }
     }
   }
@@ -2618,7 +2628,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsJSArgArray)
   tmp->ReleaseJSObjects();
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsJSArgArray)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(nsJSArgArray)
diff --git a/dom/base/nsJSTimeoutHandler.cpp b/dom/base/nsJSTimeoutHandler.cpp
index 8736cd1dd..ce5d58385 100644
--- a/dom/base/nsJSTimeoutHandler.cpp
+++ b/dom/base/nsJSTimeoutHandler.cpp
@@ -151,7 +151,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsJSScriptTimeoutHandler)
 
   if (tmp->mFunction) {
     NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mFunction)
-    NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
   }
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
diff --git a/dom/base/nsNodeUtils.cpp b/dom/base/nsNodeUtils.cpp
index ecea95dc1..75d408151 100644
--- a/dom/base/nsNodeUtils.cpp
+++ b/dom/base/nsNodeUtils.cpp
@@ -297,6 +297,16 @@ nsNodeUtils::LastRelease(nsINode* aNode)
                                          NodeWillBeDestroyed, (aNode));
     }
 
+    if (aNode->IsElement()) {
+      Element* elem = aNode->AsElement();
+      FragmentOrElement::nsDOMSlots* domSlots =
+        static_cast<FragmentOrElement::nsDOMSlots*>(slots);
+      for (auto iter = domSlots->mRegisteredIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+        DOMIntersectionObserver* observer = iter.Key();
+        observer->UnlinkTarget(*elem);
+      }
+    }
+
     delete slots;
     aNode->mSlots = nullptr;
   }
diff --git a/dom/base/nsObjectLoadingContent.cpp b/dom/base/nsObjectLoadingContent.cpp
index 709c7aa56..c1b732258 100644
--- a/dom/base/nsObjectLoadingContent.cpp
+++ b/dom/base/nsObjectLoadingContent.cpp
@@ -1582,7 +1582,6 @@ nsObjectLoadingContent::MaybeRewriteYoutubeEmbed(nsIURI* aURI, nsIURI* aBaseURI,
     }
   }
 
-  // If we're pref'd off, return after telemetry has been logged.
   if (!Preferences::GetBool(kPrefYoutubeRewrite)) {
     return;
   }
diff --git a/dom/base/nsRange.cpp b/dom/base/nsRange.cpp
index 4b4ce7885..d45a2c975 100644
--- a/dom/base/nsRange.cpp
+++ b/dom/base/nsRange.cpp
@@ -351,7 +351,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsRange)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEndParent)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRoot)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSelection)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(nsRange)
diff --git a/dom/base/nsScriptLoader.cpp b/dom/base/nsScriptLoader.cpp
index 0eb5bbf31..1e23d6c5f 100644
--- a/dom/base/nsScriptLoader.cpp
+++ b/dom/base/nsScriptLoader.cpp
@@ -353,7 +353,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsModuleScript)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mLoader)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(nsModuleScript)
diff --git a/dom/base/nsWrapperCache.cpp b/dom/base/nsWrapperCache.cpp
index b91d86598..c5993fe7b 100644
--- a/dom/base/nsWrapperCache.cpp
+++ b/dom/base/nsWrapperCache.cpp
@@ -133,7 +133,7 @@ nsWrapperCache::CheckCCWrapperTraversal(void* aScriptObjectHolder,
   // see through the COM layer, so we use a suppression to help it.
   JS::AutoSuppressGCAnalysis suppress;
 
-  aTracer->Traverse(aScriptObjectHolder, callback);
+  aTracer->TraverseNativeAndJS(aScriptObjectHolder, callback);
   MOZ_ASSERT(callback.mFound,
              "Cycle collection participant didn't traverse to preserved "
              "wrapper! This will probably crash.");
diff --git a/dom/base/nsWrapperCache.h b/dom/base/nsWrapperCache.h
index 3c69a7ec4..56cae89ed 100644
--- a/dom/base/nsWrapperCache.h
+++ b/dom/base/nsWrapperCache.h
@@ -331,8 +331,7 @@ private:
    * causes between the native object and the JS object, so it is important that
    * any native object that supports preserving of its wrapper
    * traces/traverses/unlinks the cached JS object (see
-   * NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER,
-   * NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS and
+   * NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER and
    * NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER).
    */
   enum { WRAPPER_BIT_PRESERVED = 1 << 0 };
@@ -383,7 +382,6 @@ NS_DEFINE_STATIC_IID_ACCESSOR(nsWrapperCache, NS_WRAPPERCACHE_IID)
     NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER   \
   NS_IMPL_CYCLE_COLLECTION_UNLINK_END                   \
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(_class)       \
-    NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS    \
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END                 \
   NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(_class)
 
@@ -395,7 +393,6 @@ NS_DEFINE_STATIC_IID_ACCESSOR(nsWrapperCache, NS_WRAPPERCACHE_IID)
   NS_IMPL_CYCLE_COLLECTION_UNLINK_END                      \
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(_class)          \
     NS_IMPL_CYCLE_COLLECTION_TRAVERSE(__VA_ARGS__)         \
-    NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS       \
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END                    \
   NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(_class)