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

ppapi/cpp/instance.h

Index: ppapi/cpp/instance.h
diff --git a/ppapi/cpp/instance.h b/ppapi/cpp/instance.h
index 48bca905c90c6d1c29660c0fdc273e300a48b4b4..6bf4e839381c3d371f0af86f88effabb37b31f21 100644
--- a/ppapi/cpp/instance.h
+++ b/ppapi/cpp/instance.h
@@ -244,6 +244,12 @@ class Instance {
   /// JavaScript execution will not be blocked while HandleMessage() is
   /// processing the message.
   ///
+  /// 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. If the reference
+  /// graph has cycles, the message will not be sent and an error will be logged
+  /// to the console.
+  ///
   /// <strong>Example:</strong>
   ///
   /// The following JavaScript code invokes <code>HandleMessage</code>, passing
@@ -264,9 +270,10 @@ class Instance {
   ///
   /// Refer to PostMessage() for sending messages to JavaScript.
   ///
-  /// @param[in] message A <code>Var</code> containing the data sent from
-  /// JavaScript. Message can have an int32_t, double, bool, or string value
-  /// (objects are not supported).
+  /// @param[in] message A <code>Var</code> which has been converted from a
+  /// JavaScript value. JavaScript array/object types are supported from Chrome
+  /// M29 onward. All JavaScript values are copied when passing them to the
+  /// plugin.
   virtual void HandleMessage(const Var& message);
 
   /// @}
@@ -453,6 +460,11 @@ class Instance {
   ///
   /// The browser will pop-up an alert saying "Hello world!"
   ///
+  /// When passing array or dictionary <code>PP_Var</code>s, the entire
+  /// reference graph will be converted and transferred. If the reference graph
+  /// has cycles, the message will not be sent and an error will be logged to
+  /// the console.
+  ///
   /// Listeners for message events in JavaScript code will receive an object
   /// conforming to the HTML 5 <code>MessageEvent</code> interface.
   /// Specifically, the value of message will be contained as a property called
@@ -466,9 +478,9 @@ class Instance {
   /// Refer to HandleMessage() for receiving events from JavaScript.
   ///
   /// @param[in] message A <code>Var</code> containing the data to be sent to
-  /// JavaScript. Message can have a numeric, boolean, or string value; arrays
-  /// and dictionaries are not yet supported. Ref-counted var types are copied,
-  /// and are therefore not shared between the instance and the browser.
+  /// JavaScript. Message can have a numeric, boolean, or string value.
+  /// Array/Dictionary types are supported from Chrome M29 onward.
+  /// All var types are copied when passing them to JavaScript.
   void PostMessage(const Var& message);
 
   /// @}