--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -598,50 +598,55 @@ nsStyleOutline::CalcDifference(const nsS
 // --------------------
 // nsStyleList
 //
 nsStyleList::nsStyleList(const nsPresContext* aContext)
   : mListStylePosition(NS_STYLE_LIST_STYLE_POSITION_OUTSIDE)
 {
   MOZ_COUNT_CTOR(nsStyleList);
   if (aContext->StyleSet()->IsServo()) {
-    // FIXME: bug 1328319.
-    mCounterStyle =
-      CounterStyleManager::GetBuiltinStyle(NS_STYLE_LIST_STYLE_DISC);
+    mListStyleType = nsGkAtoms::disc;
   } else {
     mCounterStyle = aContext->
       CounterStyleManager()->BuildCounterStyle(nsGkAtoms::disc);
   }
   SetQuotesInitial();
 }
 
 nsStyleList::~nsStyleList()
 {
   MOZ_COUNT_DTOR(nsStyleList);
 }
 
 nsStyleList::nsStyleList(const nsStyleList& aSource)
   : mListStylePosition(aSource.mListStylePosition)
   , mListStyleImage(aSource.mListStyleImage)
+  , mListStyleType(aSource.mListStyleType)
   , mCounterStyle(aSource.mCounterStyle)
   , mQuotes(aSource.mQuotes)
   , mImageRegion(aSource.mImageRegion)
 {
   MOZ_COUNT_CTOR(nsStyleList);
 }
 
 void
 nsStyleList::FinishStyle(nsPresContext* aPresContext)
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(aPresContext->StyleSet()->IsServo());
 
   if (mListStyleImage && !mListStyleImage->IsResolved()) {
     mListStyleImage->Resolve(aPresContext);
   }
+  if (mListStyleType) {
+    MOZ_ASSERT(!mCounterStyle);
+    mCounterStyle = aPresContext->
+      CounterStyleManager()->BuildCounterStyle(mListStyleType);
+    mListStyleType = nullptr;
+  }
 }
 
 void
 nsStyleList::SetQuotesInherit(const nsStyleList* aOther)
 {
   mQuotes = aOther->mQuotes;
 }
 
@@ -699,17 +704,18 @@ nsStyleList::CalcDifference(const nsStyl
       (mQuotes || aNewData.mQuotes) &&
       GetQuotePairs() != aNewData.GetQuotePairs()) {
     return nsChangeHint_ReconstructFrame;
   }
   if (mListStylePosition != aNewData.mListStylePosition) {
     return nsChangeHint_ReconstructFrame;
   }
   if (DefinitelyEqualImages(mListStyleImage, aNewData.mListStyleImage) &&
-      mCounterStyle == aNewData.mCounterStyle) {
+      (mCounterStyle == aNewData.mCounterStyle ||
+       mListStyleType != aNewData.mListStyleType)) {
     if (mImageRegion.IsEqualInterior(aNewData.mImageRegion)) {
       return nsChangeHint(0);
     }
     if (mImageRegion.width == aNewData.mImageRegion.width &&
         mImageRegion.height == aNewData.mImageRegion.height) {
       return NS_STYLE_HINT_VISUAL;
     }
   }

--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -1471,26 +1471,47 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsSt
 
   imgRequestProxy* GetListStyleImage() const
   {
     return mListStyleImage ? mListStyleImage->get() : nullptr;
   }
 
   already_AddRefed<nsIURI> GetListStyleImageURI() const;
 
+  // The following two methods are called from Servo code to maintain
+  // list-style-type off main thread.
+  void SetListStyleType(nsIAtom* aType)
+  {
+    mListStyleType = aType;
+    mCounterStyle = nullptr;
+  }
+  void CopyListStyleTypeFrom(const nsStyleList& aOther)
+  {
+    mListStyleType = aOther.mListStyleType;
+    mCounterStyle = aOther.mCounterStyle;
+  }
+
   const nsStyleQuoteValues::QuotePairArray& GetQuotePairs() const;
 
   void SetQuotesInherit(const nsStyleList* aOther);
   void SetQuotesInitial();
   void SetQuotesNone();
   void SetQuotes(nsStyleQuoteValues::QuotePairArray&& aValues);
 
   uint8_t mListStylePosition;                  // [inherited]
   RefPtr<nsStyleImageRequest> mListStyleImage; // [inherited]
+
+  // mCounterStyle is the actual field for computed list-style-type.
+  // mListStyleType is only used when we are off the main thread, so we
+  // cannot safely construct CounterStyle object. FinishStyle() will
+  // use it to setup mCounterStyle and then clear it. At any time, only
+  // one of the following two fields should be non-null.
+  nsCOMPtr<nsIAtom> mListStyleType;
   mozilla::CounterStylePtr mCounterStyle;      // [inherited]
+
 private:
   RefPtr<nsStyleQuoteValues> mQuotes;   // [inherited]
   nsStyleList& operator=(const nsStyleList& aOther) = delete;
 public:
   nsRect        mImageRegion;           // [inherited] the rect to use within an image
 
 private:
   // nsStyleQuoteValues objects representing two common values, for sharing.