Revert of Remove IPC::BrokerableAttachment.

ppapi/proxy/nacl_message_scanner.cc

Index: ppapi/proxy/nacl_message_scanner.cc
diff --git a/ppapi/proxy/nacl_message_scanner.cc b/ppapi/proxy/nacl_message_scanner.cc
index 19edce26768e4ef656cec321ae7acdb3a71d1a6d..e31ee38bf739fb513cd33107648e81b2e15998f7 100644
--- a/ppapi/proxy/nacl_message_scanner.cc
+++ b/ppapi/proxy/nacl_message_scanner.cc
@@ -63,6 +63,7 @@
     // Now write the handle itself in POSIX style.
     // See ParamTraits<FileDescriptor>::Read for where these values are read.
     msg->WriteBool(true);  // valid == true
+    msg->WriteBool(false);  // brokerable == false
     msg->WriteInt(handle_index);
   }
 }