--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@@ -918,17 +918,16 @@ FrameLayerBuilder::RemoveFrameFromLayerM
     if (t) {
       ThebesDisplayItemLayerUserData* thebesData =
           static_cast<ThebesDisplayItemLayerUserData*>(t->GetUserData(&gThebesDisplayItemLayerUserData));
       if (thebesData) {
         nsRegion old = data->mGeometry->ComputeInvalidationRegion();
         nsIntRegion rgn = old.ScaleToOutsidePixels(thebesData->mXScale, thebesData->mYScale, thebesData->mAppUnitsPerDevPixel);
         rgn.MoveBy(-GetTranslationForThebesLayer(t));
         thebesData->mRegionToInvalidate.Or(thebesData->mRegionToInvalidate, rgn);
-        thebesData->mRegionToInvalidate.SimplifyOutward(8);
       }
     }
 
     data->mParent->mDisplayItems.RemoveEntry(data);
   }
 
   arrayCopy.Clear();
   delete array;