Don't send PP_Vars/V8 values with cycles across PostMessage

ppapi/api/ppp_messaging.idl

Index: ppapi/api/ppp_messaging.idl
diff --git a/ppapi/api/ppp_messaging.idl b/ppapi/api/ppp_messaging.idl
index 150f7712c15656867cb43df7e4ce3f4f5da8de6c..1282b2a7b038391374307c6f572711ea5578b14b 100644
--- a/ppapi/api/ppp_messaging.idl
+++ b/ppapi/api/ppp_messaging.idl
@@ -36,10 +36,9 @@ interface PPP_Messaging {
    *
    * When converting JavaScript arrays, any object properties whose name
    * is not an array index are ignored. When passing arrays and objects, the
-   * entire reference graph will be converted and transferred, including
-   * reference cycles if they exist. Since <code>PP_Var</code>s are ref-counted,
-   * the author of the plugin must take care if they expect to receive vars with
-   * cycles. Cycles must be manually broken to correctly release the vars.
+   * entire reference graph will be converted and transferred. If the reference
+   * graph has cycles, the var will be dropped and an error will be logged to
+   * the console.
    *
    * The following JavaScript code invokes <code>HandleMessage</code>, passing
    * the module instance on which it was invoked, with <code>message</code>