diff --git a/layout/base/nsDisplayList.cpp b/layout/base/nsDisplayList.cpp
index 099eafcb5928..8da71f208451 100644
--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -3708,6 +3708,7 @@ nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
   , mScrollFrame(aScrollFrame)
   , mScrolledFrame(aScrolledFrame)
   , mScrollParentId(aBuilder->GetCurrentScrollParentId())
+  , mDisplayPortContentsOpaque(false)
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_CTOR(nsDisplayScrollLayer);
@@ -3726,6 +3727,7 @@ nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
   , mScrollFrame(aScrollFrame)
   , mScrolledFrame(aScrolledFrame)
   , mScrollParentId(aBuilder->GetCurrentScrollParentId())
+  , mDisplayPortContentsOpaque(false)
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_CTOR(nsDisplayScrollLayer);
@@ -3743,6 +3745,7 @@ nsDisplayScrollLayer::nsDisplayScrollLayer(nsDisplayListBuilder* aBuilder,
   , mScrollFrame(aScrollFrame)
   , mScrolledFrame(aScrolledFrame)
   , mScrollParentId(aBuilder->GetCurrentScrollParentId())
+  , mDisplayPortContentsOpaque(false)
 {
 #ifdef NS_BUILD_REFCNT_LOGGING
   MOZ_COUNT_CTOR(nsDisplayScrollLayer);
@@ -3770,6 +3773,22 @@ nsDisplayScrollLayer::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
   return nsDisplayWrapList::GetBounds(aBuilder, aSnap);
 }
 
+nsRect
+nsDisplayScrollLayer::GetScrolledContentRectToDraw(nsDisplayListBuilder* aBuilder,
+                                                   nsRect* aDisplayPort)
+{
+  if (aDisplayPort) {
+    // The visible region for the children may be much bigger than the hole we
+    // are viewing the children from, so that the compositor process has enough
+    // content to asynchronously pan while content is being refreshed.
+    // XXX mScrollFrame seems wrong here; we should add the offset of the
+    // scrollport
+    return *aDisplayPort + mScrollFrame->GetOffsetToCrossDoc(ReferenceFrame());
+  }
+  bool snap;
+  return GetBounds(aBuilder, &snap);
+}
+
 already_AddRefed<Layer>
 nsDisplayScrollLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
                                  LayerManager* aManager,
@@ -3786,9 +3805,26 @@ nsDisplayScrollLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
   RecordFrameMetrics(mScrolledFrame, mScrollFrame, ReferenceFrame(), layer,
                      viewport, false, false, aContainerParameters);
 
+  if (mList.IsOpaque()) {
+    nsRect displayport;
+    bool usingDisplayport =
+      nsLayoutUtils::GetDisplayPort(mScrolledFrame->GetContent(), &displayport);
+    mDisplayPortContentsOpaque = mList.GetBounds(aBuilder).Contains(
+        GetScrolledContentRectToDraw(aBuilder, usingDisplayport ? &displayport : nullptr));
+  } else {
+    mDisplayPortContentsOpaque = false;
+  }
+
   return layer.forget();
 }
 
+bool
+nsDisplayScrollLayer::IsConstructingScrollLayerForScrolledFrame(const nsIFrame* aScrolledFrame)
+{
+  FrameProperties props = aScrolledFrame->Properties();
+  return reinterpret_cast<intptr_t>(props.Get(nsIFrame::ScrollLayerCount())) != 0;
+}
+
 bool
 nsDisplayScrollLayer::ShouldBuildLayerEvenIfInvisible(nsDisplayListBuilder* aBuilder)
 {
@@ -3807,20 +3843,12 @@ nsDisplayScrollLayer::ComputeVisibility(nsDisplayListBuilder* aBuilder,
   nsRect displayport;
   bool usingDisplayPort =
     nsLayoutUtils::GetDisplayPort(mScrolledFrame->GetContent(), &displayport);
-  nsRegion childVisibleRegion;
-  if (usingDisplayPort) {
-    // The visible region for the children may be much bigger than the hole we
-    // are viewing the children from, so that the compositor process has enough
-    // content to asynchronously pan while content is being refreshed.
-    childVisibleRegion = displayport + mScrollFrame->GetOffsetToCrossDoc(ReferenceFrame());
-  } else {
-    bool snap;
-    childVisibleRegion = GetBounds(aBuilder, &snap);
-  }
+  nsRect scrolledContentRect = GetScrolledContentRectToDraw(aBuilder,
+      usingDisplayPort ? &displayport : nullptr);
 
-  nsRect boundedRect =
-    childVisibleRegion.GetBounds().Intersect(mList.GetBounds(aBuilder));
+  nsRect boundedRect = scrolledContentRect.Intersect(mList.GetBounds(aBuilder));
   nsRect allowExpansion = boundedRect.Intersect(aAllowVisibleRegionExpansion);
+  nsRegion childVisibleRegion = scrolledContentRect;
   bool visible = mList.ComputeVisibilityForSublist(
     aBuilder, &childVisibleRegion, boundedRect, allowExpansion,
     usingDisplayPort ? mScrollFrame : nullptr);
diff --git a/layout/base/nsDisplayList.h b/layout/base/nsDisplayList.h
index 384ed0ab03b2..1e712c285d73 100644
--- a/layout/base/nsDisplayList.h
+++ b/layout/base/nsDisplayList.h
@@ -3041,6 +3041,8 @@ public:
   // after merging, all the nsDisplayScrollLayers should flatten away.
   intptr_t GetScrollLayerCount();
 
+  static bool IsConstructingScrollLayerForScrolledFrame(const nsIFrame* aScrolledFrame);
+
   virtual nsIFrame* GetScrollFrame() { return mScrollFrame; }
   virtual nsIFrame* GetScrolledFrame() { return mScrolledFrame; }
 
@@ -3048,10 +3050,16 @@ public:
   virtual void WriteDebugInfo(nsACString& aTo) MOZ_OVERRIDE;
 #endif
 
+  bool IsDisplayPortOpaque() { return mDisplayPortContentsOpaque; }
+
 protected:
+  nsRect GetScrolledContentRectToDraw(nsDisplayListBuilder* aBuilder,
+                                      nsRect* aDisplayPort);
+
   nsIFrame* mScrollFrame;
   nsIFrame* mScrolledFrame;
   ViewID mScrollParentId;
+  bool mDisplayPortContentsOpaque;
 };
 
 /**