diff -r 000000000000 -r 6474c204b198 editor/idl/nsIEditorStyleSheets.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/editor/idl/nsIEditorStyleSheets.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,91 @@
+/* -*- 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 "nsISupports.idl"
+
+%{C++
+class nsCSSStyleSheet;
+%}
+
+[ptr] native nsCSSStyleSheet(nsCSSStyleSheet);
+
+[scriptable, uuid(4805e682-49b9-11d3-9ce4-ed60bd6cb5bc)]
+
+interface nsIEditorStyleSheets : nsISupports
+{
+  /** Load and apply the style sheet, specified by aURL, to the
+    * editor's document, replacing the last style sheet added (if any).
+    * This is always asynchronous, and may cause network I/O.
+    * 
+    * @param aURL The style sheet to be loaded and applied.
+    */
+  void replaceStyleSheet(in AString aURL);
+
+  /** Add the given style sheet to the editor's document,
+    * on top of any that are already there.
+    * This is always asynchronous, and may cause network I/O.
+    *
+    * @param aURL The style sheet to be loaded and applied.
+    */
+  void addStyleSheet(in AString aURL);
+
+  /** Load and apply the override style sheet, specified by aURL, to the
+    * editor's document, replacing the last override style sheet added (if any).
+    * This is always synchronous, so aURL should be a local file with only
+    * local @imports. This action is not undoable. It is not intended for
+    * "user" style sheets, only for editor developers to add sheets to change
+    * display behavior for editing (like showing special cursors) that will
+    * not be affected by loading "document" style sheets with addStyleSheet or
+    * especially replaceStyleSheet.
+    * 
+    * @param aURL The style sheet to be loaded and applied.
+    */
+  void replaceOverrideStyleSheet(in AString aURL);
+
+  /** Load and apply an override style sheet, specified by aURL, to
+    * the editor's document, on top of any that are already there.
+    * This is always synchronous, so the same caveats about local files and no
+    * non-local @import as replaceOverrideStyleSheet apply here, too.
+    *
+    * @param aURL The style sheet to be loaded and applied.
+    */
+  void addOverrideStyleSheet(in AString aURL);
+
+  /** Remove the given style sheet from the editor's document
+    * This is always synchronous
+    *
+    * @param aURL The style sheet to be removed
+    */
+  void removeStyleSheet(in AString aURL);
+
+  /** Remove the given override style sheet from the editor's document
+    * This is always synchronous
+    *
+    * @param aURL The style sheet to be removed.
+    */
+  void removeOverrideStyleSheet(in AString aURL);
+
+  /** Enable or disable the given style sheet from the editor's document
+    * This is always synchronous
+    *
+    * @param aURL  The style sheet to be enabled or disabled
+    * @param aEnable true to enable, or false to disable the style sheet
+    */
+  void enableStyleSheet(in AString aURL, in boolean aEnable);
+
+  /** Get the nsCSSStyleSheet associated with the given URL.
+    *
+    * @param aURL         The style sheet's URL
+    * @return             the style sheet
+    */
+  [noscript] nsCSSStyleSheet getStyleSheetForURL(in AString aURL);
+
+  /** Get the URL associated with the given nsCSSStyleSheet.
+    *
+    * @param aStyleSheet  The style sheet
+    * @return             the style sheet's URL
+    */
+  [noscript] AString getURLForStyleSheet(in nsCSSStyleSheet aStyleSheet);
+};