diff --git a/layout/base/public/nsFrameList.h b/layout/base/public/nsFrameList.h
index 5a06078ebfc..e69de29bb2d 100644
--- a/layout/base/public/nsFrameList.h
+++ b/layout/base/public/nsFrameList.h
@@ -1,164 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is Mozilla Communicator client code.
- *
- * The Initial Developer of the Original Code is
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1998
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either of the GNU General Public License Version 2 or later (the "GPL"),
- * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
-#ifndef nsFrameList_h___
-#define nsFrameList_h___
-
-#include "nsIFrame.h"
-
-/**
- * A class for managing a singly linked list of frames. Frames are
- * linked together through their next-sibling pointer.
- */
-class nsFrameList {
-public:
-  nsFrameList() {
-    mFirstChild = nsnull;
-  }
-
-  nsFrameList(nsIFrame* aHead) {
-    mFirstChild = aHead;
-  }
-
-  ~nsFrameList() {
-  }
-
-  void DestroyFrames(nsPresContext* aPresContext);
-
-  void SetFrames(nsIFrame* aFrameList) {
-    mFirstChild = aFrameList;
-  }
-
-  void AppendFrames(nsIFrame* aParent, nsIFrame* aFrameList);
-
-  void AppendFrames(nsIFrame* aParent, nsFrameList& aFrameList) {
-    AppendFrames(aParent, aFrameList.mFirstChild);
-    aFrameList.mFirstChild = nsnull;
-  }
-
-  void AppendFrame(nsIFrame* aParent, nsIFrame* aFrame);
-
-  // Take aFrame out of the frame list. This also disconnects aFrame
-  // from the sibling list. This will return PR_FALSE if aFrame is
-  // nsnull or if aFrame is not in the list.
-  PRBool RemoveFrame(nsIFrame* aFrame);
-
-  // Remove the first child from the list. The caller is assumed to be
-  // holding a reference to the first child. This call is equivalent
-  // in behavior to calling RemoveFrame(FirstChild()).
-  PRBool RemoveFirstChild();
-
-  // Take aFrame out of the frame list and then destroy it. This also
-  // disconnects aFrame from the sibling list. This will return
-  // PR_FALSE if aFrame is nsnull or if aFrame is not in the list.
-  PRBool DestroyFrame(nsPresContext* aPresContext, nsIFrame* aFrame);
-
-  void InsertFrame(nsIFrame* aParent,
-                   nsIFrame* aPrevSibling,
-                   nsIFrame* aNewFrame);
-
-  void InsertFrames(nsIFrame* aParent,
-                    nsIFrame* aPrevSibling,
-                    nsIFrame* aFrameList);
-
-  void InsertFrames(nsIFrame* aParent, nsIFrame* aPrevSibling,
-                    nsFrameList& aFrameList) {
-    InsertFrames(aParent, aPrevSibling, aFrameList.FirstChild());
-    aFrameList.mFirstChild = nsnull;
-  }
-
-  PRBool ReplaceFrame(nsPresContext* aPresContext,
-                      nsIFrame* aParent,
-                      nsIFrame* aOldFrame,
-                      nsIFrame* aNewFrame,
-                      PRBool aDestroy);
-
-  PRBool Split(nsIFrame* aAfterFrame, nsIFrame** aNextFrameResult);
-
-  nsIFrame* PullFrame(nsIFrame* aParent,
-                      nsIFrame* aLastChild,
-                      nsFrameList& aFromList);
-
-  nsIFrame* FirstChild() const {
-    return mFirstChild;
-  }
-
-  nsIFrame* LastChild() const;
-
-  nsIFrame* FrameAt(PRInt32 aIndex) const;
-
-  PRBool IsEmpty() const {
-    return nsnull == mFirstChild;
-  }
-
-  PRBool NotEmpty() const {
-    return nsnull != mFirstChild;
-  }
-
-  PRBool ContainsFrame(const nsIFrame* aFrame) const;
-
-  PRInt32 GetLength() const;
-
-  nsIFrame* GetPrevSiblingFor(nsIFrame* aFrame) const;
-
-#ifdef IBMBIDI
-  /**
-   * Return the frame before this frame in visual order (after Bidi reordering)
-   */
-  nsIFrame* GetPrevVisualFor(nsIFrame* aFrame) const;
-
-  /**
-   * Return the frame after this frame in visual order (after Bidi reordering)
-   */
-  nsIFrame* GetNextVisualFor(nsIFrame* aFrame) const;
-#endif // IBMBIDI
-
-  void VerifyParent(nsIFrame* aParent) const;
-
-#ifdef NS_DEBUG
-  void List(nsPresContext* aPresContext, FILE* out) const;
-#endif
-
-private:
-  PRBool DoReplaceFrame(nsIFrame* aParent,
-                        nsIFrame* aOldFrame,
-                        nsIFrame* aNewFrame);
-  
-protected:
-  nsIFrame* mFirstChild;
-};
-
-#endif /* nsFrameList_h___ */
diff --git a/layout/base/src/nsFrameList.cpp b/layout/base/src/nsFrameList.cpp
index 0b684d2edde..e69de29bb2d 100644
--- a/layout/base/src/nsFrameList.cpp
+++ b/layout/base/src/nsFrameList.cpp
@@ -1,595 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is Mozilla Communicator client code.
- *
- * The Initial Developer of the Original Code is
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1998
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- *   Pierre Phaneuf <pp@ludusdesign.com>
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either of the GNU General Public License Version 2 or later (the "GPL"),
- * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
-#include "nsFrameList.h"
-#ifdef NS_DEBUG
-#include "nsIFrameDebug.h"
-#endif
-
-#ifdef IBMBIDI
-#include "nsCOMPtr.h"
-#include "nsLayoutAtoms.h"
-#include "nsILineIterator.h"
-
-/**
- * Helper class for comparing the location of frames. Used by
- * GetPrevVisualFor() and GetNextVisualFor()
- */
-#define LINE_MIN 0
-#define XCOORD_MIN 0x80000000
-#define MY_LINE_MAX 0x7fffffff
-#define XCOORD_MAX 0x7fffffff
-class nsFrameOrigin {
-public:
-  // default constructor
-  nsFrameOrigin() {
-    mLine = 0;
-    mXCoord = 0;
-  }
-
-  nsFrameOrigin(PRInt32 line, nscoord xCoord) {
-    mLine = line;
-    mXCoord = xCoord;
-  }
-
-  // copy constructor
-  nsFrameOrigin(const nsFrameOrigin& aFrameOrigin) {
-    mLine = aFrameOrigin.mLine;
-    mXCoord = aFrameOrigin.mXCoord;
-  }
-
-  ~nsFrameOrigin() {
-  }
-
-  nsFrameOrigin& operator=(const nsFrameOrigin& aFrameOrigin) { 
-    mLine = aFrameOrigin.mLine;
-    mXCoord = aFrameOrigin.mXCoord;
-    return *this;
-  }
-
-  PRBool operator<(const nsFrameOrigin& aFrameOrigin) {
-    if (mLine < aFrameOrigin.mLine) {
-      return PR_TRUE;
-    }
-    if (mLine > aFrameOrigin.mLine) {
-      return PR_FALSE;
-    }
-    if (mXCoord < aFrameOrigin.mXCoord) {
-      return PR_TRUE;
-    }
-    return PR_FALSE;
-  }
-  
-  PRBool operator>(const nsFrameOrigin& aFrameOrigin) {
-    if (mLine > aFrameOrigin.mLine) {
-      return PR_TRUE;
-    }
-    if (mLine < aFrameOrigin.mLine) {
-      return PR_FALSE;
-    }
-    if (mXCoord > aFrameOrigin.mXCoord) {
-      return PR_TRUE;
-    }
-    return PR_FALSE;
-  }
-
-  PRBool operator==(const nsFrameOrigin& aFrameOrigin) {
-    if (aFrameOrigin.mLine == mLine && aFrameOrigin.mXCoord == mXCoord) {
-      return PR_TRUE;
-    }
-    return PR_FALSE;
-  }
-
-protected:
-  PRInt32 mLine;
-  nscoord mXCoord;
-};
-#endif // IBMBIDI
-
-void
-nsFrameList::DestroyFrames(nsPresContext* aPresContext)
-{
-  nsIFrame* next;
-  for (nsIFrame* frame = mFirstChild; frame; frame = next) {
-    next = frame->GetNextSibling();
-    frame->Destroy(aPresContext);
-    mFirstChild = next;
-  }
-}
-
-void
-nsFrameList::AppendFrames(nsIFrame* aParent, nsIFrame* aFrameList)
-{
-  NS_PRECONDITION(nsnull != aFrameList, "null ptr");
-  if (nsnull != aFrameList) {
-    nsIFrame* lastChild = LastChild();
-    if (nsnull == lastChild) {
-      mFirstChild = aFrameList;
-    }
-    else {
-      lastChild->SetNextSibling(aFrameList);
-    }
-    if (aParent) {
-      for (nsIFrame* frame = aFrameList; frame;
-           frame = frame->GetNextSibling()) {
-        frame->SetParent(aParent);
-      }
-    }
-  }
-}
-
-void
-nsFrameList::AppendFrame(nsIFrame* aParent, nsIFrame* aFrame)
-{
-  NS_PRECONDITION(nsnull != aFrame, "null ptr");
-  if (nsnull != aFrame) {
-    nsIFrame* lastChild = LastChild();
-    if (nsnull == lastChild) {
-      mFirstChild = aFrame;
-    }
-    else {
-      lastChild->SetNextSibling(aFrame);
-    }
-    if (nsnull != aParent) {
-      aFrame->SetParent(aParent);
-    }
-  }
-}
-
-PRBool
-nsFrameList::RemoveFrame(nsIFrame* aFrame)
-{
-  NS_PRECONDITION(nsnull != aFrame, "null ptr");
-  if (nsnull != aFrame) {
-    nsIFrame* nextFrame = aFrame->GetNextSibling();
-    aFrame->SetNextSibling(nsnull);
-    if (aFrame == mFirstChild) {
-      mFirstChild = nextFrame;
-      return PR_TRUE;
-    }
-    else {
-      nsIFrame* prevSibling = GetPrevSiblingFor(aFrame);
-      if (prevSibling) {
-        prevSibling->SetNextSibling(nextFrame);
-        return PR_TRUE;
-      }
-    }
-  }
-  // aFrame was not in the list. 
-  return PR_FALSE;
-}
-
-PRBool
-nsFrameList::RemoveFirstChild()
-{
-  if (mFirstChild) {
-    nsIFrame* nextFrame = mFirstChild->GetNextSibling();
-    mFirstChild->SetNextSibling(nsnull);
-    mFirstChild = nextFrame;
-    return PR_TRUE;
-  }
-  return PR_FALSE;
-}
-
-PRBool
-nsFrameList::DestroyFrame(nsPresContext* aPresContext, nsIFrame* aFrame)
-{
-  NS_PRECONDITION(nsnull != aFrame, "null ptr");
-  if (RemoveFrame(aFrame)) {
-    aFrame->Destroy(aPresContext);
-    return PR_TRUE;
-  }
-  return PR_FALSE;
-}
-
-void
-nsFrameList::InsertFrame(nsIFrame* aParent,
-                         nsIFrame* aPrevSibling,
-                         nsIFrame* aNewFrame)
-{
-  NS_PRECONDITION(nsnull != aNewFrame, "null ptr");
-  if (nsnull != aNewFrame) {
-    if (nsnull == aPrevSibling) {
-      aNewFrame->SetNextSibling(mFirstChild);
-      mFirstChild = aNewFrame;
-    }
-    else {
-      nsIFrame* nextFrame = aPrevSibling->GetNextSibling();
-      aPrevSibling->SetNextSibling(aNewFrame);
-      aNewFrame->SetNextSibling(nextFrame);
-    }
-    if (aParent) {
-      aNewFrame->SetParent(aParent);
-    }
-  }
-}
-
-void
-nsFrameList::InsertFrames(nsIFrame* aParent,
-                          nsIFrame* aPrevSibling,
-                          nsIFrame* aFrameList)
-{
-  NS_PRECONDITION(nsnull != aFrameList, "null ptr");
-  if (nsnull != aFrameList) {
-    nsIFrame* lastNewFrame = nsnull;
-    if (aParent) {
-      for (nsIFrame* frame = aFrameList; frame;
-           frame = frame->GetNextSibling()) {
-        frame->SetParent(aParent);
-        lastNewFrame = frame;
-      }
-    }
-
-    // Get the last new frame if necessary
-    if (!lastNewFrame) {
-      nsFrameList tmp(aFrameList);
-      lastNewFrame = tmp.LastChild();
-    }
-
-    // Link the new frames into the child list
-    if (nsnull == aPrevSibling) {
-      lastNewFrame->SetNextSibling(mFirstChild);
-      mFirstChild = aFrameList;
-    }
-    else {
-      nsIFrame* nextFrame = aPrevSibling->GetNextSibling();
-      aPrevSibling->SetNextSibling(aFrameList);
-      lastNewFrame->SetNextSibling(nextFrame);
-    }
-  }
-}
-
-PRBool
-nsFrameList::DoReplaceFrame(nsIFrame* aParent,
-                            nsIFrame* aOldFrame,
-                            nsIFrame* aNewFrame)
-{
-  NS_PRECONDITION(aOldFrame, "null ptr");
-  NS_PRECONDITION(aNewFrame, "null ptr");
-  if (!aOldFrame || !aNewFrame) {
-    return PR_FALSE;
-  }
-  
-  nsIFrame* nextFrame = aOldFrame->GetNextSibling();
-  if (aOldFrame == mFirstChild) {
-    mFirstChild = aNewFrame;
-  }
-  else {
-    nsIFrame* prevSibling = GetPrevSiblingFor(aOldFrame);
-    if (!prevSibling) {
-      NS_WARNING("nsFrameList::ReplaceFrame: aOldFrame not found in list");
-      return PR_FALSE;
-    }
-    prevSibling->SetNextSibling(aNewFrame);
-  }
-
-  aNewFrame->SetNextSibling(nextFrame);
-  
-  if (aParent) {
-    aNewFrame->SetParent(aParent);
-  }
-  return PR_TRUE;
-}
-
-PRBool
-nsFrameList::ReplaceFrame(nsPresContext* aPresContext,
-                          nsIFrame* aParent,
-                          nsIFrame* aOldFrame,
-                          nsIFrame* aNewFrame,
-                          PRBool aDestroy)
-{
-  NS_PRECONDITION(aOldFrame, "null ptr");
-  NS_PRECONDITION(aNewFrame, "null ptr");
-  if (DoReplaceFrame(aParent, aOldFrame, aNewFrame)) {
-    if (aDestroy) {
-      aOldFrame->Destroy(aPresContext);
-    }
-    return PR_TRUE;
-  }
-  return PR_FALSE;
-}
-
-PRBool
-nsFrameList::Split(nsIFrame* aAfterFrame, nsIFrame** aNextFrameResult)
-{
-  NS_PRECONDITION(nsnull != aAfterFrame, "null ptr");
-  NS_PRECONDITION(nsnull != aNextFrameResult, "null ptr");
-  NS_ASSERTION(ContainsFrame(aAfterFrame), "split after unknown frame");
-
-  if (aNextFrameResult && aAfterFrame) {
-    nsIFrame* nextFrame = aAfterFrame->GetNextSibling();
-    aAfterFrame->SetNextSibling(nsnull);
-    *aNextFrameResult = nextFrame;
-    return PR_TRUE;
-  }
-  return PR_FALSE;
-}
-
-nsIFrame*
-nsFrameList::PullFrame(nsIFrame* aParent,
-                       nsIFrame* aLastChild,
-                       nsFrameList& aFromList)
-{
-  NS_PRECONDITION(nsnull != aParent, "null ptr");
-
-  nsIFrame* pulledFrame = nsnull;
-  if (nsnull != aParent) {
-    pulledFrame = aFromList.FirstChild();
-    if (nsnull != pulledFrame) {
-      // Take frame off old list
-      aFromList.RemoveFirstChild();
-
-      // Put it on the end of this list
-      if (nsnull == aLastChild) {
-        NS_ASSERTION(nsnull == mFirstChild, "bad aLastChild");
-        mFirstChild = pulledFrame;
-      }
-      else {
-        aLastChild->SetNextSibling(pulledFrame);
-      }
-      pulledFrame->SetParent(aParent);
-    }
-  }
-  return pulledFrame;
-}
-
-nsIFrame*
-nsFrameList::LastChild() const
-{
-  nsIFrame* frame = mFirstChild;
-  if (!frame) {
-    return nsnull;
-  }
-
-  nsIFrame* next = frame->GetNextSibling();
-  while (next) {
-    frame = next;
-    next = frame->GetNextSibling();
-  }
-  return frame;
-}
-
-nsIFrame*
-nsFrameList::FrameAt(PRInt32 aIndex) const
-{
-  NS_PRECONDITION(aIndex >= 0, "invalid arg");
-  if (aIndex < 0) return nsnull;
-  nsIFrame* frame = mFirstChild;
-  while ((aIndex-- > 0) && frame) {
-    frame = frame->GetNextSibling();
-  }
-  return frame;
-}
-
-PRBool
-nsFrameList::ContainsFrame(const nsIFrame* aFrame) const
-{
-  NS_PRECONDITION(nsnull != aFrame, "null ptr");
-  nsIFrame* frame = mFirstChild;
-  while (frame) {
-    if (frame == aFrame) {
-      return PR_TRUE;
-    }
-    frame = frame->GetNextSibling();
-  }
-  return PR_FALSE;
-}
-
-PRInt32
-nsFrameList::GetLength() const
-{
-  PRInt32 count = 0;
-  nsIFrame* frame = mFirstChild;
-  while (frame) {
-    count++;
-    frame = frame->GetNextSibling();
-  }
-  return count;
-}
-
-nsIFrame*
-nsFrameList::GetPrevSiblingFor(nsIFrame* aFrame) const
-{
-  NS_PRECONDITION(nsnull != aFrame, "null ptr");
-  if (aFrame == mFirstChild) {
-    return nsnull;
-  }
-  nsIFrame* frame = mFirstChild;
-  while (frame) {
-    nsIFrame* next = frame->GetNextSibling();
-    if (next == aFrame) {
-      break;
-    }
-    frame = next;
-  }
-  return frame;
-}
-
-void
-nsFrameList::VerifyParent(nsIFrame* aParent) const
-{
-#ifdef NS_DEBUG
-  for (nsIFrame* frame = mFirstChild; frame;
-       frame = frame->GetNextSibling()) {
-    NS_ASSERTION(frame->GetParent() == aParent, "bad parent");
-  }
-#endif
-}
-
-#ifdef NS_DEBUG
-void
-nsFrameList::List(nsPresContext* aPresContext, FILE* out) const
-{
-  fputs("<\n", out);
-  for (nsIFrame* frame = mFirstChild; frame;
-       frame = frame->GetNextSibling()) {
-    nsIFrameDebug*  frameDebug;
-    if (NS_SUCCEEDED(frame->QueryInterface(NS_GET_IID(nsIFrameDebug), (void**)&frameDebug))) {
-      frameDebug->List(aPresContext, out, 1);
-    }
-  }
-  fputs(">\n", out);
-}
-#endif
-
-#ifdef IBMBIDI
-nsIFrame*
-nsFrameList::GetPrevVisualFor(nsIFrame* aFrame) const
-{
-  NS_PRECONDITION(nsnull != aFrame, "null ptr");
-  nsILineIterator* iter;
-
-  if (aFrame->GetType() == nsLayoutAtoms::blockFrame)
-    return GetPrevSiblingFor(aFrame);
-
-  nsIFrame* frame;
-  nsIFrame* furthestFrame = nsnull;
-
-  frame = mFirstChild;
-
-  nsIFrame* blockFrame = aFrame->GetParent();
-  if (!blockFrame)
-    return GetPrevSiblingFor(aFrame);
-  nsresult result = blockFrame->QueryInterface(NS_GET_IID(nsILineIterator), (void**)&iter);
-  if (NS_FAILED(result) || !iter) { // If the parent is not a block frame, just check all the siblings
-
-    PRInt32 maxX, limX;
-    maxX = -0x7fffffff;
-    limX = aFrame->GetRect().x;
-    while (frame) {
-      nsRect tempRect = frame->GetRect();
-      if (tempRect.x > maxX && tempRect.x < limX) { // we are looking for the highest value less than the current one
-        maxX = tempRect.x;
-        furthestFrame = frame;
-      }
-      frame = frame->GetNextSibling();
-    }
-    return furthestFrame;
-
-  }
-
-  // Otherwise use the LineIterator to check the siblings on this line and the previous line
-  if (!blockFrame || !iter)
-    return nsnull;
-
-  nsFrameOrigin maxOrig(LINE_MIN, XCOORD_MIN);
-  PRInt32 testLine, thisLine;
-
-  result = iter->FindLineContaining(aFrame, &thisLine);
-  if (NS_FAILED(result) || thisLine < 0)
-    return nsnull;
-
-  nsFrameOrigin limOrig(thisLine, aFrame->GetRect().x);
-
-  while (frame) {
-    if (NS_SUCCEEDED(iter->FindLineContaining(frame, &testLine))
-        && testLine >= 0
-        && (testLine == thisLine || testLine == thisLine - 1)) {
-      nsFrameOrigin testOrig(testLine, frame->GetRect().x);
-      if (testOrig > maxOrig && testOrig < limOrig) { // we are looking for the highest value less than the current one
-        maxOrig = testOrig;
-        furthestFrame = frame;
-      }
-    }
-    frame = frame->GetNextSibling();
-  }
-  return furthestFrame;
-}
-
-nsIFrame*
-nsFrameList::GetNextVisualFor(nsIFrame* aFrame) const
-{
-  NS_PRECONDITION(nsnull != aFrame, "null ptr");
-  nsILineIterator* iter;
-
-  if (aFrame->GetType() == nsLayoutAtoms::blockFrame) {
-    return aFrame->GetNextSibling();
-  }
-
-  nsIFrame* frame;
-  nsIFrame* nearestFrame = nsnull;
-
-  frame = mFirstChild;
-
-  nsIFrame* blockFrame = aFrame->GetParent();
-  if (!blockFrame)
-    return GetPrevSiblingFor(aFrame);
-  nsresult result = blockFrame->QueryInterface(NS_GET_IID(nsILineIterator), (void**)&iter);
-  if (NS_FAILED(result) || !iter) { // If the parent is not a block frame, just check all the siblings
-
-    PRInt32 minX, limX;
-    minX = 0x7fffffff;
-    limX = aFrame->GetRect().x;
-    while (frame) {
-      nsRect tempRect = frame->GetRect();
-      if (tempRect.x < minX && tempRect.x > limX) { // we are looking for the lowest value greater than the current one
-        minX = tempRect.x;
-        nearestFrame = frame;
-      }
-      frame = frame->GetNextSibling();
-    }
-    return nearestFrame;
-  }
-
-  // Otherwise use the LineIterator to check the siblings on this line and the previous line
-  if (!blockFrame || !iter)
-    return nsnull;
-
-  nsFrameOrigin minOrig(MY_LINE_MAX, XCOORD_MAX);
-  PRInt32 testLine, thisLine;
-
-  result = iter->FindLineContaining(aFrame, &thisLine);
-  if (NS_FAILED(result) || thisLine < 0)
-    return nsnull;
-
-  nsFrameOrigin limOrig(thisLine, aFrame->GetRect().x);
-
-  while (frame) {
-    if (NS_SUCCEEDED(iter->FindLineContaining(frame, &testLine))
-        && testLine >= 0
-        && (testLine == thisLine || testLine == thisLine + 1)) {
-      nsFrameOrigin testOrig(testLine, frame->GetRect().x);
-      if (testOrig < minOrig && testOrig > limOrig) { // we are looking for the lowest value greater than the current one
-        minOrig = testOrig;
-        nearestFrame = frame;
-      }
-    }
-    frame = frame->GetNextSibling();
-  }
-  return nearestFrame;
-}
-#endif
diff --git a/layout/generic/nsFrameList.cpp b/layout/generic/nsFrameList.cpp
index 0b684d2edde..592a27a462f 100644
--- a/layout/generic/nsFrameList.cpp
+++ b/layout/generic/nsFrameList.cpp
@@ -150,6 +150,9 @@ nsFrameList::AppendFrames(nsIFrame* aParent, nsIFrame* aFrameList)
       }
     }
   }
+#ifdef DEBUG
+  CheckForLoops();
+#endif
 }
 
 void
@@ -168,6 +171,9 @@ nsFrameList::AppendFrame(nsIFrame* aParent, nsIFrame* aFrame)
       aFrame->SetParent(aParent);
     }
   }
+#ifdef DEBUG
+  CheckForLoops();
+#endif
 }
 
 PRBool
@@ -236,6 +242,9 @@ nsFrameList::InsertFrame(nsIFrame* aParent,
       aNewFrame->SetParent(aParent);
     }
   }
+#ifdef DEBUG
+  CheckForLoops();
+#endif
 }
 
 void
@@ -271,6 +280,9 @@ nsFrameList::InsertFrames(nsIFrame* aParent,
       lastNewFrame->SetNextSibling(nextFrame);
     }
   }
+#ifdef DEBUG
+  CheckForLoops();
+#endif
 }
 
 PRBool
@@ -302,6 +314,9 @@ nsFrameList::DoReplaceFrame(nsIFrame* aParent,
   if (aParent) {
     aNewFrame->SetParent(aParent);
   }
+#ifdef DEBUG
+  CheckForLoops();
+#endif
   return PR_TRUE;
 }
 
@@ -364,6 +379,9 @@ nsFrameList::PullFrame(nsIFrame* aParent,
       pulledFrame->SetParent(aParent);
     }
   }
+#ifdef DEBUG
+  CheckForLoops();
+#endif
   return pulledFrame;
 }
 
@@ -593,3 +611,31 @@ nsFrameList::GetNextVisualFor(nsIFrame* aFrame) const
   return nearestFrame;
 }
 #endif
+
+#ifdef DEBUG
+void
+nsFrameList::CheckForLoops()
+{
+  if (!mFirstChild) {
+    return;
+  }
+  
+  // Simple algorithm to find a loop in a linked list -- advance pointers
+  // through it at speeds of 1 and 2, and if they ever get to be equal bail
+  nsIFrame *first = mFirstChild, *second = mFirstChild;
+  do {
+    first = first->GetNextSibling();
+    second = second->GetNextSibling();
+    if (!second) {
+      break;
+    }
+    second = second->GetNextSibling();
+    if (first == second) {
+      // Loop detected!  Since second advances faster, they can't both be null;
+      // we would have broken out of the loop long ago.
+      NS_ERROR("loop in frame list.  This will probably hang soon.");
+      break;
+    }                           
+  } while (first && second);
+}
+#endif
diff --git a/layout/generic/nsFrameList.h b/layout/generic/nsFrameList.h
index 5a06078ebfc..a0fd7bba556 100644
--- a/layout/generic/nsFrameList.h
+++ b/layout/generic/nsFrameList.h
@@ -51,6 +51,9 @@ public:
 
   nsFrameList(nsIFrame* aHead) {
     mFirstChild = aHead;
+#ifdef DEBUG
+    CheckForLoops();
+#endif
   }
 
   ~nsFrameList() {
@@ -60,6 +63,9 @@ public:
 
   void SetFrames(nsIFrame* aFrameList) {
     mFirstChild = aFrameList;
+#ifdef DEBUG
+    CheckForLoops();
+#endif
   }
 
   void AppendFrames(nsIFrame* aParent, nsIFrame* aFrameList);
@@ -156,6 +162,10 @@ private:
   PRBool DoReplaceFrame(nsIFrame* aParent,
                         nsIFrame* aOldFrame,
                         nsIFrame* aNewFrame);
+
+#ifdef DEBUG
+  void CheckForLoops();
+#endif
   
 protected:
   nsIFrame* mFirstChild;