--- a/layout/base/DisplayItemClip.cpp
+++ b/layout/base/DisplayItemClip.cpp
@@ -398,20 +398,18 @@ DisplayItemClip::GetCommonRoundedRectCou
     }
   }
   return clipCount;
 }
 
 void
 DisplayItemClip::AppendRoundedRects(nsTArray<RoundedRect>* aArray, uint32_t aCount) const
 {
-  uint32_t count = std::min(mRoundedClipRects.Length(), size_t(aCount));
-  for (uint32_t i = 0; i < count; ++i) {
-    *aArray->AppendElement() = mRoundedClipRects[i];
-  }
+  size_t count = std::min(mRoundedClipRects.Length(), size_t(aCount));
+  aArray->AppendElements(mRoundedClipRects.Elements(), count);
 }
 
 bool
 DisplayItemClip::ComputeRegionInClips(DisplayItemClip* aOldClip,
                                       const nsPoint& aShift,
                                       nsRegion* aCombined) const
 {
   if (!mHaveClipRect || (aOldClip && !aOldClip->mHaveClipRect)) {