--- a/editor/libeditor/html/nsHTMLEditRules.cpp
+++ b/editor/libeditor/html/nsHTMLEditRules.cpp
@@ -8930,20 +8930,20 @@ nsHTMLEditRules::RelativeChangeIndentati
     }
     else {
       mHTMLEditor->mHTMLCSSUtils->RemoveCSSProperty(element, marginProperty, value, false);
       // remove unnecessary DIV blocks:
       // we could skip this section but that would cause a FAIL in
       // editor/libeditor/html/tests/browserscope/richtext.html, which expects
       // to unapply a CSS "indent" (<div style="margin-left: 40px;">) by
       // removing the DIV container instead of just removing the CSS property.
-      nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-      if (nsHTMLEditUtils::IsDiv(aNode)
-          && (node != mHTMLEditor->GetActiveEditingHost())
-          && mHTMLEditor->IsNodeInActiveEditor(aNode)) {
+      nsCOMPtr<dom::Element> node = do_QueryInterface(aNode);
+      if (node && node->IsHTML(nsGkAtoms::div) &&
+          node != mHTMLEditor->GetActiveEditingHost() &&
+          mHTMLEditor->IsNodeInActiveEditor(node)) {
         // we deal with an editable DIV;
         // let's see if it is useless and if we can remove it
         nsCOMPtr<nsIDOMNamedNodeMap> attributeList;
         res = element->GetAttributes(getter_AddRefs(attributeList));
         NS_ENSURE_SUCCESS(res, res);
         PRUint32 count;
         attributeList->GetLength(&count);
         if (!count) {

--- a/editor/libeditor/html/nsHTMLEditor.cpp
+++ b/editor/libeditor/html/nsHTMLEditor.cpp
@@ -3990,39 +3990,36 @@ void nsHTMLEditor::IsTextPropertySetByCo
 // Note: Table Editing methods are implemented in nsTableEditor.cpp
 //
 
 
 bool
 nsHTMLEditor::IsNodeInActiveEditor(nsIDOMNode* aNode)
 {
   nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
-  if (!node) {
-    return false;
-  }
+  return node && IsNodeInActiveEditor(node);
+}
+
+bool
+nsHTMLEditor::IsNodeInActiveEditor(nsINode* aNode)
+{
   nsIContent* activeEditingHost = GetActiveEditingHost();
   if (!activeEditingHost) {
     return false;
   }
-  return nsContentUtils::ContentIsDescendantOf(node, activeEditingHost);
+  return nsContentUtils::ContentIsDescendantOf(aNode, activeEditingHost);
 }
 
 bool
 nsHTMLEditor::SetCaretInTableCell(nsIDOMElement* aElement)
 {
-  if (!aElement || !IsNodeInActiveEditor(aElement)) {
-    return false;
-  }
-
   nsCOMPtr<dom::Element> element = do_QueryInterface(aElement);
-  if (!element || !element->IsHTML()) {
-    return false;
-  }
-
-  if (!nsHTMLEditUtils::IsTableElement(element)) {
+  if (!element || !element->IsHTML() ||
+      !nsHTMLEditUtils::IsTableElement(element) ||
+      !IsNodeInActiveEditor(element)) {
     return false;
   }
 
   nsIContent* node = element;
   while (node->HasChildren()) {
     node = node->GetFirstChild();
   }
 

--- a/editor/libeditor/html/nsHTMLEditor.h
+++ b/editor/libeditor/html/nsHTMLEditor.h
@@ -442,16 +442,17 @@ protected:
   // Get the focused node of this editor.
   // @return    If the editor has focus, this returns the focused node.
   //            Otherwise, returns null.
   already_AddRefed<nsINode> GetFocusedNode();
 
   // Return TRUE if aElement is a table-related elemet and caret was set
   bool SetCaretInTableCell(nsIDOMElement* aElement);
   bool IsNodeInActiveEditor(nsIDOMNode* aNode);
+  bool IsNodeInActiveEditor(nsINode* aNode);
 
   // key event helpers
   NS_IMETHOD TabInTable(bool inIsShift, bool *outHandled);
   NS_IMETHOD CreateBR(nsIDOMNode *aNode, PRInt32 aOffset, 
                       nsCOMPtr<nsIDOMNode> *outBRNode, nsIEditor::EDirection aSelect = nsIEditor::eNone);
 
 // Table Editing (implemented in nsTableEditor.cpp)