diff --git a/layout/base/FrameLayerBuilder.cpp b/layout/base/FrameLayerBuilder.cpp
index 2032abe7b22b..49253dba06cc 100644
--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@@ -2735,7 +2735,6 @@ ContainerState::ProcessDisplayItems(nsDisplayList* aList,
   }
 
   aList->AppendToTop(&savedItems);
-  aList->SetDidComputeVisibility();
 }
 
 void
diff --git a/layout/base/nsDisplayList.cpp b/layout/base/nsDisplayList.cpp
index fe00f1e91a3d..c6a8e8288779 100644
--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -1227,9 +1227,6 @@ nsDisplayList::ComputeVisibilityForSublist(nsDisplayListBuilder* aBuilder,
 
   mIsOpaque = !aVisibleRegion->Intersects(mVisibleRect);
   mForceTransparentSurface = forceTransparentSurface;
-#if defined(DEBUG) || defined(MOZ_DUMP_PAINTING)
-  mDidComputeVisibility = true;
-#endif
   return anyVisible;
 }
 
diff --git a/layout/base/nsDisplayList.h b/layout/base/nsDisplayList.h
index 91462cb3f5f3..bac37e68a7c7 100644
--- a/layout/base/nsDisplayList.h
+++ b/layout/base/nsDisplayList.h
@@ -1433,14 +1433,12 @@ public:
   /**
    * Create an empty list.
    */
-  nsDisplayList() :
-    mIsOpaque(false)
+  nsDisplayList()
+    : mIsOpaque(false)
+    , mForceTransparentSurface(false)
   {
     mTop = &mSentinel;
     mSentinel.mAbove = nullptr;
-#if defined(DEBUG) || defined(MOZ_DUMP_PAINTING)
-    mDidComputeVisibility = false;
-#endif
   }
   ~nsDisplayList() {
     if (mSentinel.mAbove) {
@@ -1626,16 +1624,13 @@ public:
    * empty, i.e. everything visible in this list is opaque.
    */
   bool IsOpaque() const {
-    NS_ASSERTION(mDidComputeVisibility, "Need to have called ComputeVisibility");
     return mIsOpaque;
   }
 
   /**
-   * Returns true if during ComputeVisibility any display item
-   * set the surface to be transparent.
+   * Returns true if any display item requires the surface to be transparent.
    */
   bool NeedsTransparentSurface() const {
-    NS_ASSERTION(mDidComputeVisibility, "Need to have called ComputeVisibility");
     return mForceTransparentSurface;
   }
   /**
@@ -1700,16 +1695,6 @@ public:
    */
   nsRect GetVisibleRect() const;
 
-#if defined(DEBUG) || defined(MOZ_DUMP_PAINTING)
-  bool DidComputeVisibility() const { return mDidComputeVisibility; }
-#endif
-
-  void SetDidComputeVisibility()
-  {
-#if defined(DEBUG) || defined(MOZ_DUMP_PAINTING)
-    mDidComputeVisibility = true;
-#endif
-  }
   void SetIsOpaque()
   {
     mIsOpaque = true;
@@ -1739,9 +1724,6 @@ private:
   // This is set to true by FrameLayerBuilder if any display item in this
   // list needs to force the surface containing this list to be transparent.
   bool mForceTransparentSurface;
-#if defined(DEBUG) || defined(MOZ_DUMP_PAINTING)
-  bool mDidComputeVisibility;
-#endif
 };
 
 /**
diff --git a/layout/base/nsLayoutDebugger.cpp b/layout/base/nsLayoutDebugger.cpp
index ff7cb9119b8a..1096ef4cca83 100644
--- a/layout/base/nsLayoutDebugger.cpp
+++ b/layout/base/nsLayoutDebugger.cpp
@@ -154,10 +154,7 @@ PrintDisplayItemTo(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem,
   nsRect component = aItem->GetComponentAlphaBounds(aBuilder);
   nsDisplayList* list = aItem->GetChildren();
   const DisplayItemClip& clip = aItem->GetClip();
-  nsRegion opaque;
-  if (!list || list->DidComputeVisibility()) {
-    opaque = aItem->GetOpaqueRegion(aBuilder, &snap);
-  }
+  nsRegion opaque = aItem->GetOpaqueRegion(aBuilder, &snap);
   if (aDumpHtml && aItem->Painted()) {
     nsCString string(aItem->Name());
     string.Append('-');