msctf: Define ITfEditSession implemented by TextServices.
diff --git a/include/msctf.idl b/include/msctf.idl
index 40853ee..91b11c3 100644
--- a/include/msctf.idl
+++ b/include/msctf.idl
@@ -713,3 +713,14 @@
 
     HRESULT OnLanguageChanged();
 }
+
+[
+  object,
+  uuid(aa80e803-2021-11d2-93e0-0060b067b86e),
+  pointer_default(unique)
+]
+interface ITfEditSession : IUnknown
+{
+    HRESULT DoEditSession(
+        [in] TfEditCookie ec);
+}