Bug 731293. Add nsLayoutUtils::GetParentOrPlaceholderForCrossDoc. r=mats

layout/base/nsLayoutUtils.cpp

@@ -2109,11 +2109,21 @@ nsLayoutUtils::GetParentOrPlaceholderFor(nsIFrame* aFrame)
 {
   if ((aFrame->GetStateBits() & NS_FRAME_OUT_OF_FLOW)
       && !aFrame->GetPrevInFlow()) {
-    return aFrame->PresContext()->PresShell()->FrameManager()->GetPlaceholderFrameFor(aFrame);
+    return aFrame->PresContext()->PresShell()->FrameManager()->
+      GetPlaceholderFrameFor(aFrame);
   }
   return aFrame->GetParent();
 }
 
+nsIFrame*
+nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(nsIFrame* aFrame)
+{
+  nsIFrame* f = GetParentOrPlaceholderFor(aFrame);
+  if (f)
+    return f;
+  return GetCrossDocParentFrame(aFrame);
+}
+
 nsIFrame*
 nsLayoutUtils::GetNextContinuationOrSpecialSibling(nsIFrame *aFrame)
 {

layout/base/nsLayoutUtils.h

@@ -811,6 +811,12 @@ public:
    */
   static nsIFrame* GetParentOrPlaceholderFor(nsIFrame* aFrame);
 
+  /**
+   * If aFrame is an out of flow frame, return its placeholder, otherwise
+   * return its (possibly cross-doc) parent.
+   */
+  static nsIFrame* GetParentOrPlaceholderForCrossDoc(nsIFrame* aFrame);
+
   /**
    * Get a frame's next-in-flow, or, if it doesn't have one, its special sibling.
    */