Actually free plugin implement vars when running out of process when the

ppapi/c/dev/ppb_var_deprecated.h

 /* Copyright (c) 2010 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_PPB_VAR_DEPRECATED_H_
 #define PPAPI_C_PPB_VAR_DEPRECATED_H_
 
 #include "ppapi/c/dev/deprecated_bool.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_module.h"
@@ skipping 188 matching lines @@
    * true and sets *object_data to the value passed to CreateObject provided
    * object_data is non-NULL. Otherwise, this method returns false.
    */
   bool (*IsInstanceOf)(struct PP_Var var,
                        const struct PPP_Class_Deprecated* object_class,
                        void** object_data);
 
   /**
    * Creates an object that the plugin implements. The plugin supplies a
    * pointer to the class interface it implements for that object, and its
-   * associated internal data that represents that object.
+   * associated internal data that represents that object. This object data
+   * must be unique among all "live" objects.
    *
    * The returned object will have a reference count of 1. When the reference
    * count reached 0, the class' Destruct function wlil be called.
    *
    * On failure, this will return a null var. This probably means the module
    * was invalid.
    *
    * Example: Say we're implementing a "Point" object.
    * <pre>  void PointDestruct(void* object) {
    *     delete (Point*)object;
@@ skipping 24 matching lines @@
       const struct PPP_Class_Deprecated* object_class,
       void* object_data);
 };
 
 /**
  * @}
  * End addtogroup PPB
  */
 #endif  /* PPAPI_C_PPB_VAR_DEPRECATED_H_ */