Support using a Mojo message pipe in a ChannelHandle.

ipc/ipc_mojo_param_traits.h

Index: ipc/ipc_mojo_param_traits.h
diff --git a/ipc/ipc_mojo_param_traits.h b/ipc/ipc_mojo_param_traits.h
index a474f7b1df9a9dbb5ef5882a47d96aae1e9f7dd8..8c4fd18b0a3c7625c141c7518700fd5caceb2b04 100644
--- a/ipc/ipc_mojo_param_traits.h
+++ b/ipc/ipc_mojo_param_traits.h
@@ -13,6 +13,7 @@
 
 namespace base {
 class PickleIterator;
+class PickleSizer;
 }
 
 namespace IPC {
@@ -22,6 +23,7 @@ class Message;
 template <>
 struct IPC_EXPORT ParamTraits<mojo::MessagePipeHandle> {
   typedef mojo::MessagePipeHandle param_type;
+  static void GetSize(base::PickleSizer* sizer, const param_type& p);
   static void Write(Message* m, const param_type& p);
   static bool Read(const Message* m, base::PickleIterator* iter, param_type* r);
   static void Log(const param_type& p, std::string* l);