Ensure that PP_Instance values are unique within a plugin process in addition...

ppapi/c/private/ppb_proxy_private.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_C_PRIVATE_PROXY_PRIVATE_H_
 #define PPAPI_C_PRIVATE_PROXY_PRIVATE_H_
 
+#include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_module.h"
 #include "ppapi/c/pp_resource.h"
 
-#define PPB_PROXY_PRIVATE_INTERFACE "PPB_Proxy_Private;2"
+#define PPB_PROXY_PRIVATE_INTERFACE "PPB_Proxy_Private;3"
 
 // Exposes functions needed by the out-of-process proxy to call into the
 // renderer PPAPI implementation.
 struct PPB_Proxy_Private {
   // Called when the given plugin process has crashed.
   void (*PluginCrashed)(PP_Module module);
 
   // Returns the instance for the given resource, or 0 on failure.
   PP_Instance (*GetInstanceForResource)(PP_Resource resource);
+
+  // Sets a callback that will be used to make sure that PP_Instance IDs
+  // are unique in the plugin.
+  //
+  // Since the plugin may be shared between several browser processes, we need
+  // to do extra work to make sure that an instance ID is globally unqiue. The
+  // given function will be called and will return true if the given
+  // PP_Instance is OK to use in the plugin. It will then be marked as "in use"
+  // On failure (returns false), the host implementation will generate a new
+  // instance ID and try again.
+  void (*SetReserveInstanceIDCallback)(
+      PP_Module module,
+      PP_Bool (*is_seen)(PP_Module, PP_Instance));
 };
 
 #endif  // PPAPI_C_PRIVATE_PROXY_PRIVATE_H_