diff --git a/gfx/layers/LayerTreeInvalidation.cpp b/gfx/layers/LayerTreeInvalidation.cpp
index 728a64a4f780..af24930625ff 100644
--- a/gfx/layers/LayerTreeInvalidation.cpp
+++ b/gfx/layers/LayerTreeInvalidation.cpp
@@ -115,7 +115,7 @@ struct LayerPropertiesBase : public LayerProperties
     }
 
     result = result.Union(ComputeChangeInternal(aCallback));
-    result = result.Union(TransformRect(mLayer->GetInvalidRegion().GetBounds(), mTransform));
+    result = result.Union(TransformRect(mLayer->GetInvalidRect(), mTransform));
 
     if (mMaskLayer && otherMask) {
       nsIntRect maskDiff = mMaskLayer->ComputeChange(aCallback);
diff --git a/gfx/layers/Layers.h b/gfx/layers/Layers.h
index 9ae81e9333c5..07dd81a50011 100644
--- a/gfx/layers/Layers.h
+++ b/gfx/layers/Layers.h
@@ -923,23 +923,23 @@ public:
    * Returns the current area of the layer (in layer-space coordinates)
    * marked as needed to be recomposited.
    */
-  const nsIntRegion& GetInvalidRegion() { return mInvalidRegion; }
+  const nsIntRect& GetInvalidRect() { return mInvalidRect; }
 
   /**
    * Mark the entirety of the layer's visible region as being invalid.
    */
-  void SetInvalidRectToVisibleRegion() { mInvalidRegion = GetVisibleRegion(); }
+  void SetInvalidRectToVisibleRegion() { mInvalidRect = GetVisibleRegion().GetBounds(); }
 
   /**
    * Adds to the current invalid rect.
    */
-  void AddInvalidRect(const nsIntRect& aRect) { mInvalidRegion.Or(mInvalidRegion, aRect); }
+  void AddInvalidRect(const nsIntRect& aRect) { mInvalidRect = mInvalidRect.Union(aRect); }
 
   /**
    * Clear the invalid rect, marking the layer as being identical to what is currently
    * composited.
    */
-  void ClearInvalidRect() { mInvalidRegion.SetEmpty(); }
+  void ClearInvalidRect() { mInvalidRect.SetEmpty(); }
 
 
 #ifdef DEBUG
@@ -1006,13 +1006,13 @@ protected:
   float mOpacity;
   nsIntRect mClipRect;
   nsIntRect mTileSourceRect;
+  nsIntRect mInvalidRect;
   PRUint32 mContentFlags;
   bool mUseClipRect;
   bool mUseTileSourceRect;
   bool mIsFixedPosition;
   gfxPoint mAnchor;
   DebugOnly<PRUint32> mDebugColorIndex;
-  nsIntRegion mInvalidRegion;
 };
 
 /**
diff --git a/gfx/layers/basic/BasicThebesLayer.h b/gfx/layers/basic/BasicThebesLayer.h
index 27fd8773f0ce..77f62094361f 100644
--- a/gfx/layers/basic/BasicThebesLayer.h
+++ b/gfx/layers/basic/BasicThebesLayer.h
@@ -37,9 +37,8 @@ public:
   {
     NS_ASSERTION(BasicManager()->InConstruction(),
                  "Can only set properties in construction phase");
-    mInvalidRegion.Or(mInvalidRegion, aRegion);
-    mInvalidRegion.SimplifyOutward(10);
-    mValidRegion.Sub(mValidRegion, mInvalidRegion);
+    mValidRegion.Sub(mValidRegion, aRegion);
+    AddInvalidRect(aRegion.GetBounds());
   }
 
   virtual void PaintThebes(gfxContext* aContext,
diff --git a/gfx/layers/d3d10/ThebesLayerD3D10.cpp b/gfx/layers/d3d10/ThebesLayerD3D10.cpp
index 1f1ede0f91e1..3f4906b07b44 100644
--- a/gfx/layers/d3d10/ThebesLayerD3D10.cpp
+++ b/gfx/layers/d3d10/ThebesLayerD3D10.cpp
@@ -53,9 +53,8 @@ void
 
 ThebesLayerD3D10::InvalidateRegion(const nsIntRegion &aRegion)
 {
-  mInvalidRegion.Or(mInvalidRegion, aRegion);
-  mInvalidRegion.SimplifyOutward(10);
-  mValidRegion.Sub(mValidRegion, mInvalidRegion);
+  mValidRegion.Sub(mValidRegion, aRegion);
+  AddInvalidRect(aRegion.GetBounds());
 }
 
 void ThebesLayerD3D10::CopyRegion(ID3D10Texture2D* aSrc, const nsIntPoint &aSrcOffset,
diff --git a/gfx/layers/d3d9/ThebesLayerD3D9.cpp b/gfx/layers/d3d9/ThebesLayerD3D9.cpp
index 0be6007c749f..9b973e624405 100644
--- a/gfx/layers/d3d9/ThebesLayerD3D9.cpp
+++ b/gfx/layers/d3d9/ThebesLayerD3D9.cpp
@@ -47,9 +47,8 @@ ThebesLayerD3D9::~ThebesLayerD3D9()
 void
 ThebesLayerD3D9::InvalidateRegion(const nsIntRegion &aRegion)
 {
-  mInvalidRegion.Or(mInvalidRegion, aRegion);
-  mInvalidRegion.SimplifyOutward(10);
-  mValidRegion.Sub(mValidRegion, mInvalidRegion);
+  mValidRegion.Sub(mValidRegion, aRegion);
+  AddInvalidRect(aRegion.GetBounds());
 }
 
 void
diff --git a/gfx/layers/opengl/ThebesLayerOGL.cpp b/gfx/layers/opengl/ThebesLayerOGL.cpp
index 8c33d409baee..5614c5a96578 100644
--- a/gfx/layers/opengl/ThebesLayerOGL.cpp
+++ b/gfx/layers/opengl/ThebesLayerOGL.cpp
@@ -784,9 +784,8 @@ ThebesLayerOGL::SetVisibleRegion(const nsIntRegion &aRegion)
 void
 ThebesLayerOGL::InvalidateRegion(const nsIntRegion &aRegion)
 {
-  mInvalidRegion.Or(mInvalidRegion, aRegion);
-  mInvalidRegion.SimplifyOutward(10);
-  mValidRegion.Sub(mValidRegion, mInvalidRegion);
+  mValidRegion.Sub(mValidRegion, aRegion);
+  AddInvalidRect(aRegion.GetBounds());
 }
 
 void
diff --git a/layout/base/nsDisplayList.cpp b/layout/base/nsDisplayList.cpp
index 0537cd0f3e6d..61c3bac4a7e2 100644
--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -675,8 +675,6 @@ void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
   nsIntRect invalid;
   if (props) {
     invalid = props->ComputeDifferences(root, computeInvalidFunc);
-  } else if (widgetTransaction) {
-    LayerProperties::ClearInvalidations(root);
   }
 
   if (view) {
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 1a1e4674bcc0..52236140ac7d 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -5275,8 +5275,6 @@ PresShell::Paint(nsIView*           aViewToPaint,
         nsIntRect invalid;
         if (props) {
           invalid = props->ComputeDifferences(layerManager->GetRoot(), computeInvalidFunc);
-        } else {
-          LayerProperties::ClearInvalidations(layerManager->GetRoot());
         }
         if (!invalid.IsEmpty()) {
           if (props) {