Bug 1110277 patch 2 - Add nsLayoutUtils::LastContinuationOrIBSplitSibling(). r=bzbarsky

This is used in patch 3.

layout/base/nsLayoutUtils.cpp

@@ -3907,6 +3907,25 @@ nsLayoutUtils::FirstContinuationOrIBSplitSibling(nsIFrame *aFrame)
   return result;
 }
 
+nsIFrame*
+nsLayoutUtils::LastContinuationOrIBSplitSibling(nsIFrame *aFrame)
+{
+  nsIFrame *result = aFrame->FirstContinuation();
+  if (result->GetStateBits() & NS_FRAME_PART_OF_IBSPLIT) {
+    while (true) {
+      nsIFrame *f = static_cast<nsIFrame*>
+        (result->Properties().Get(nsIFrame::IBSplitSibling()));
+      if (!f)
+        break;
+      result = f;
+    }
+  }
+
+  result = result->LastContinuation();
+
+  return result;
+}
+
 bool
 nsLayoutUtils::IsFirstContinuationOrIBSplitSibling(nsIFrame *aFrame)
 {

layout/base/nsLayoutUtils.h

@@ -1253,6 +1253,13 @@ public:
   static nsIFrame*
   FirstContinuationOrIBSplitSibling(nsIFrame *aFrame);
 
+  /**
+   * Get the last frame in the continuation-plus-ib-split-sibling chain
+   * containing aFrame.
+   */
+  static nsIFrame*
+  LastContinuationOrIBSplitSibling(nsIFrame *aFrame);
+
   /**
    * Is FirstContinuationOrIBSplitSibling(aFrame) going to return
    * aFrame?