Bug 1156393 - Cache nsDisplayBorder bounds. r=roc

layout/base/nsDisplayList.cpp

@@ -3097,6 +3097,14 @@ nsDisplayCaret::Paint(nsDisplayListBuilder* aBuilder,
   mCaret->PaintCaret(aBuilder, *aCtx->GetDrawTarget(), mFrame, ToReferenceFrame());
 }
 
+nsDisplayBorder::nsDisplayBorder(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame)
+  : nsDisplayItem(aBuilder, aFrame)
+{
+  MOZ_COUNT_CTOR(nsDisplayBorder);
+
+  mBounds = CalculateBounds(*mFrame->StyleBorder());
+}
+
 bool
 nsDisplayBorder::IsInvisibleInRect(const nsRect& aRect)
 {
@@ -3155,7 +3163,7 @@ nsRect
 nsDisplayBorder::GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap)
 {
   *aSnap = true;
-  return CalculateBounds(*mFrame->StyleBorder());
+  return mBounds;
 }
 
 nsRect

layout/base/nsDisplayList.h

@@ -2149,11 +2149,8 @@ protected:
  */
 class nsDisplayBorder : public nsDisplayItem {
 public:
-  nsDisplayBorder(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame) :
-    nsDisplayItem(aBuilder, aFrame)
-  {
-    MOZ_COUNT_CTOR(nsDisplayBorder);
-  }
+  nsDisplayBorder(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame);
+
 #ifdef NS_BUILD_REFCNT_LOGGING
   virtual ~nsDisplayBorder() {
     MOZ_COUNT_DTOR(nsDisplayBorder);
@@ -2173,6 +2170,8 @@ public:
 
 protected:
   nsRect CalculateBounds(const nsStyleBorder& aStyleBorder);
+
+  nsRect mBounds;
 };
 
 /**