PPAPI: header comments on when PPP_Instance::DidDestroy and PPP_ShutdownModule

ppapi/api/ppp.idl

 /* Copyright (c) 2011 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /**
  * This file defines three functions that your module must
  * implement to interact with the browser.
  */
 
@@ skipping 52 matching lines @@
 /**
  * PPP_ShutdownModule() is <strong>sometimes</strong> called before the module
  * is unloaded. It is not recommended that you implement this function.
  *
  * There is no practical use of this function for third party modules. Its
  * existence is because of some internal use cases inside Chrome.
  *
  * Since your module runs in a separate process, there's no need to free
  * allocated memory. There is also no need to free any resources since all of
  * resources associated with an instance will be force-freed when that instance
- * is deleted. Moreover, this function will not be called when Chrome does
- * "fast shutdown" of a web page.
+ * is deleted.
+ *
+ * <strong>Note:</strong> This function will always be skipped on untrusted
+ * (Native Client) implementations. This function may be skipped on trusted
+ * implementations in certain circumstances when Chrome does "fast shutdown"
+ * of a web page.
  */
 PP_EXPORT void PPP_ShutdownModule();
 /**
  * @}
  */
 
 /**
  * @addtogroup Functions
  * @{
  */
@@ skipping 25 matching lines @@
 /**
  * @}
  */
 
 #ifdef __cplusplus
 }  /* extern "C" */
 #endif
 
 #endinl