--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@@ -673,17 +673,16 @@ struct NewLayerEntry {
     : mAnimatedGeometryRoot(nullptr)
     , mScrollClip(nullptr)
     , mLayerContentsVisibleRect(0, 0, -1, -1)
     , mLayerState(LAYER_INACTIVE)
     , mHideAllLayersBelow(false)
     , mOpaqueForAnimatedGeometryRootParent(false)
     , mPropagateComponentAlphaFlattening(true)
     , mUntransformedVisibleRegion(false)
-    , mIsPerspectiveItem(false)
   {}
   // mLayer is null if the previous entry is for a PaintedLayer that hasn't
   // been optimized to some other form (yet).
   RefPtr<Layer> mLayer;
   AnimatedGeometryRoot* mAnimatedGeometryRoot;
   const DisplayItemScrollClip* mScrollClip;
   // If non-null, this ScrollMetadata is set to the be the first ScrollMetadata
   // on the layer.
@@ -709,17 +708,16 @@ struct NewLayerEntry {
   bool mOpaqueForAnimatedGeometryRootParent;
 
   // If true, then the content flags for this layer should contribute
   // to our decision to flatten component alpha layers, false otherwise.
   bool mPropagateComponentAlphaFlattening;
   // mVisibleRegion is relative to the associated frame before
   // transform.
   bool mUntransformedVisibleRegion;
-  bool mIsPerspectiveItem;
 };
 
 class PaintedLayerDataTree;
 
 /**
  * This is tree node type for PaintedLayerDataTree.
  * Each node corresponds to a different animated geometry root, and contains
  * a stack of PaintedLayerDatas, in bottom-to-top order.
@@ -4150,19 +4148,16 @@ ContainerState::ProcessDisplayItems(nsDi
       NS_ASSERTION(FindIndexOfLayerIn(mNewChildLayers, ownLayer) < 0,
                    "Layer already in list???");
 
       NewLayerEntry* newLayerEntry = mNewChildLayers.AppendElement();
       newLayerEntry->mLayer = ownLayer;
       newLayerEntry->mAnimatedGeometryRoot = animatedGeometryRoot;
       newLayerEntry->mScrollClip = agrScrollClip;
       newLayerEntry->mLayerState = layerState;
-      if (itemType == nsDisplayItem::TYPE_PERSPECTIVE) {
-        newLayerEntry->mIsPerspectiveItem = true;
-      }
 
       // Don't attempt to flatten compnent alpha layers that are within
       // a forced active layer, or an active transform;
       if (itemType == nsDisplayItem::TYPE_TRANSFORM ||
           layerState == LAYER_ACTIVE_FORCE) {
         newLayerEntry->mPropagateComponentAlphaFlattening = false;
       }
       // nsDisplayTransform::BuildLayer must set layerContentsVisibleRect.