Revert of Remove IPC::BrokerableAttachment.

ipc/ipc_message.h

Index: ipc/ipc_message.h
diff --git a/ipc/ipc_message.h b/ipc/ipc_message.h
index 41f57afc31ce136da054fbffdf8ee990e27d7ffa..6bf18dec4254548003c3dbbeab4720165bacca64 100644
--- a/ipc/ipc_message.h
+++ b/ipc/ipc_message.h
@@ -15,6 +15,7 @@
 #include "base/pickle.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
+#include "ipc/brokerable_attachment.h"
 #include "ipc/ipc_export.h"
 
 #if !defined(NDEBUG)
@@ -207,6 +208,10 @@
       scoped_refptr<base::Pickle::Attachment>* attachment) const override;
   // Returns true if there are any attachment in this message.
   bool HasAttachments() const override;
+  // Returns true if there are any MojoHandleAttachments in this message.
+  bool HasMojoHandles() const;
+  // Whether the message has any brokerable attachments.
+  bool HasBrokerableAttachments() const;
 
 #ifdef IPC_MESSAGE_LOG_ENABLED
   // Adds the outgoing time from Time::Now() at the end of the message and sets