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

ppapi/cpp/instance.h

 // 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.
 
 #ifndef PPAPI_CPP_INSTANCE_H_
 #define PPAPI_CPP_INSTANCE_H_
 
 /// @file
 /// Defines the C++ wrapper for a plugin instance.
 ///
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   /// will be deleted. You should never delete the Instance object yourself
   /// since the lifetime is handled by the C++ wrapper and is controlled by the
   /// browser's calls to the PPP_Instance interface.
   ///
   /// The PP_Instance identifier will still be valid during this call so the
   /// plugin can perform cleanup-related tasks. Once this function returns, the
   /// PP_Instance handle will be invalid. This means that you can't do any
   /// asynchronous operations like network requests or file writes from this
   /// destructor since they will be immediately canceled.
   ///
-  /// <strong>Important note:</strong> This function may be skipped in certain
-  /// circumstances when Chrome does "fast shutdown". Fast shutdown will happen
-  /// in some cases when all plugin instances are being deleted, and no cleanup
-  /// functions will be called. The module will just be unloaded and the process
-  /// terminated.
+  /// <strong>Important note:</strong> This function will always be skipped on
+  /// untrusted (Native Client) implementations. This function may be skipped
+  /// in certain circumstances when Chrome does "fast shutdown". Fast shutdown
+  /// will happen in some cases when all plugin instances are being deleted,
+  /// and no cleanup functions will be called. The module will just be unloaded
+  /// and the process terminated.
   virtual ~Instance();
 
   /// Returns the PP_Instance identifying this object. When using the PPAPI C++
   /// wrappers this is not normally necessary, but is required when using the
   /// lower-level C APIs.
   PP_Instance pp_instance() const { return pp_instance_; }
 
   /// Initializes this plugin with the given arguments. This will be called
   /// immediately after the instance object is constructed.
   ///
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   typedef std::map<std::string, void*> InterfaceNameToObjectMap;
   InterfaceNameToObjectMap interface_name_to_objects_;
 };
 
 }  // namespace pp
 
 /// @}
 /// End addtogroup CPP
 
 #endif  // PPAPI_CPP_INSTANCE_H_