diff -r 000000000000 -r 6474c204b198 editor/libeditor/base/nsStyleSheetTxns.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/editor/libeditor/base/nsStyleSheetTxns.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,145 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+#include <stddef.h>                     // for nullptr
+
+#include "nsAString.h"
+#include "nsCOMPtr.h"                   // for nsCOMPtr, do_QueryInterface, etc
+#include "nsCSSStyleSheet.h"            // for nsCSSStyleSheet
+#include "nsDebug.h"                    // for NS_ENSURE_TRUE
+#include "nsError.h"                    // for NS_OK, etc
+#include "nsIDOMDocument.h"             // for nsIDOMDocument
+#include "nsIDocument.h"                // for nsIDocument
+#include "nsIDocumentObserver.h"        // for UPDATE_STYLE
+#include "nsIEditor.h"                  // for nsIEditor
+#include "nsStyleSheetTxns.h"
+
+class nsIStyleSheet;
+
+static void
+AddStyleSheet(nsIEditor* aEditor, nsIStyleSheet* aSheet)
+{
+  nsCOMPtr<nsIDOMDocument> domDoc;
+  aEditor->GetDocument(getter_AddRefs(domDoc));
+  nsCOMPtr<nsIDocument> doc = do_QueryInterface(domDoc);
+  if (doc) {
+    doc->BeginUpdate(UPDATE_STYLE);
+    doc->AddStyleSheet(aSheet);
+    doc->EndUpdate(UPDATE_STYLE);
+  }
+}
+
+static void
+RemoveStyleSheet(nsIEditor *aEditor, nsIStyleSheet *aSheet)
+{
+  nsCOMPtr<nsIDOMDocument> domDoc;
+  aEditor->GetDocument(getter_AddRefs(domDoc));
+  nsCOMPtr<nsIDocument> doc = do_QueryInterface(domDoc);
+  if (doc) {
+    doc->BeginUpdate(UPDATE_STYLE);
+    doc->RemoveStyleSheet(aSheet);
+    doc->EndUpdate(UPDATE_STYLE);
+  }
+}
+
+AddStyleSheetTxn::AddStyleSheetTxn()
+:  EditTxn()
+,  mEditor(nullptr)
+{
+}
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(AddStyleSheetTxn, EditTxn,
+                                   mSheet)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(AddStyleSheetTxn)
+NS_INTERFACE_MAP_END_INHERITING(EditTxn)
+
+NS_IMETHODIMP
+AddStyleSheetTxn::Init(nsIEditor *aEditor, nsCSSStyleSheet *aSheet)
+{
+  NS_ENSURE_TRUE(aEditor && aSheet, NS_ERROR_INVALID_ARG);
+
+  mEditor = aEditor;
+  mSheet = aSheet;
+
+  return NS_OK;
+}
+
+
+NS_IMETHODIMP
+AddStyleSheetTxn::DoTransaction()
+{
+  NS_ENSURE_TRUE(mEditor && mSheet, NS_ERROR_NOT_INITIALIZED);
+
+  AddStyleSheet(mEditor, mSheet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+AddStyleSheetTxn::UndoTransaction()
+{
+  NS_ENSURE_TRUE(mEditor && mSheet, NS_ERROR_NOT_INITIALIZED);
+
+  RemoveStyleSheet(mEditor, mSheet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+AddStyleSheetTxn::GetTxnDescription(nsAString& aString)
+{
+  aString.AssignLiteral("AddStyleSheetTxn");
+  return NS_OK;
+}
+
+
+RemoveStyleSheetTxn::RemoveStyleSheetTxn()
+:  EditTxn()
+,  mEditor(nullptr)
+{
+}
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(RemoveStyleSheetTxn, EditTxn,
+                                   mSheet)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(RemoveStyleSheetTxn)
+NS_INTERFACE_MAP_END_INHERITING(EditTxn)
+
+NS_IMETHODIMP
+RemoveStyleSheetTxn::Init(nsIEditor *aEditor, nsCSSStyleSheet *aSheet)
+{
+  NS_ENSURE_TRUE(aEditor && aSheet, NS_ERROR_INVALID_ARG);
+
+  mEditor = aEditor;
+  mSheet = aSheet;
+
+  return NS_OK;
+}
+
+
+NS_IMETHODIMP
+RemoveStyleSheetTxn::DoTransaction()
+{
+  NS_ENSURE_TRUE(mEditor && mSheet, NS_ERROR_NOT_INITIALIZED);
+
+  RemoveStyleSheet(mEditor, mSheet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoveStyleSheetTxn::UndoTransaction()
+{
+  NS_ENSURE_TRUE(mEditor && mSheet, NS_ERROR_NOT_INITIALIZED);
+
+  AddStyleSheet(mEditor, mSheet);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoveStyleSheetTxn::GetTxnDescription(nsAString& aString)
+{
+  aString.AssignLiteral("RemoveStyleSheetTxn");
+  return NS_OK;
+}