Bug 1958219. Remove some unused scroll parent fields. r=layout-reviewers,emilio

Differential Revision: https://phabricator.services.mozilla.com/D244302

layout/painting/nsDisplayList.cpp

@@ -5364,7 +5364,6 @@ nsDisplaySubDocument::nsDisplaySubDocument(nsDisplayListBuilder* aBuilder,
                                            nsDisplayOwnLayerFlags aFlags)
     : nsDisplayOwnLayer(aBuilder, aFrame, aList,
                         aBuilder->CurrentActiveScrolledRoot(), aFlags),
-      mScrollParentId(aBuilder->GetCurrentScrollParentId()),
       mShouldFlatten(false),
       mSubDocFrame(aSubDocFrame) {
   MOZ_COUNT_CTOR(nsDisplaySubDocument);

layout/painting/nsDisplayList.h

@@ -5503,7 +5503,6 @@ class nsDisplaySubDocument : public nsDisplayOwnLayer {
   void RemoveFrame(nsIFrame* aFrame) override;
 
  protected:
-  ViewID mScrollParentId;
   bool mForceDispatchToContentRegion{};
   bool mShouldFlatten;
   nsSubDocumentFrame* mSubDocFrame;

layout/tables/nsTableFrame.cpp

@@ -7372,8 +7372,7 @@ nsDisplayTableBackgroundSet::nsDisplayTableBackgroundSet(
     nsDisplayListBuilder* aBuilder, nsIFrame* aTable)
     : mBuilder(aBuilder),
       mColGroupBackgrounds(aBuilder),
-      mColBackgrounds(aBuilder),
-      mCurrentScrollParentId(aBuilder->GetCurrentScrollParentId()) {
+      mColBackgrounds(aBuilder) {
   mPrevTableBackgroundSet = mBuilder->SetTableBackgroundSet(this);
   mozilla::DebugOnly<const nsIFrame*> reference =
       mBuilder->FindReferenceFrameFor(aTable, &mToReferenceFrame);

layout/tables/nsTableFrame.h

@@ -95,9 +95,6 @@ class nsDisplayTableBackgroundSet {
   }
 
   const ActiveScrolledRoot* GetTableASR() { return mTableASR; }
-  layers::ScrollableLayerGuid::ViewID GetScrollParentId() {
-    return mCurrentScrollParentId;
-  }
 
  private:
   // This class is only used on stack, so we don't have to worry about leaking
@@ -114,7 +111,6 @@ class nsDisplayTableBackgroundSet {
   nsTArray<nsTableColFrame*> mColumns;
   nsPoint mToReferenceFrame;
   nsRect mDirtyRect;
-  layers::ScrollableLayerGuid::ViewID mCurrentScrollParentId;
 
   const DisplayItemClipChain* mCombinedTableClipChain;
   const ActiveScrolledRoot* mTableASR;