Dynamically generate a heading for Extension Docs API pages

chrome/common/extensions/api/app_window.idl

Index: chrome/common/extensions/api/app_window.idl
diff --git a/chrome/common/extensions/api/app_window.idl b/chrome/common/extensions/api/app_window.idl
index 594a5d6e900a464950c776e8d966a113bda21ae1..26009c5e8e4b32e492f178063588c2c2c5fe94cc 100644
--- a/chrome/common/extensions/api/app_window.idl
+++ b/chrome/common/extensions/api/app_window.idl
@@ -2,6 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Use the <code>chrome.app.window</code> module to create windows. Windows
+// have an optional frame with title bar and size controls. They are not
+// associated with any Chrome browser windows.
+
+[availability=23]
 namespace app.window {
   dictionary Bounds {
     long? left;