Remove IPC::BrokerableAttachment.

ipc/ipc_message_utils.cc

Index: ipc/ipc_message_utils.cc
diff --git a/ipc/ipc_message_utils.cc b/ipc/ipc_message_utils.cc
index f814727ee2b81fff5694adc45d94d0011d477105..be83e5a236bb2322e66b36d13aa0640759cdc691 100644
--- a/ipc/ipc_message_utils.cc
+++ b/ipc/ipc_message_utils.cc
@@ -658,8 +658,14 @@ bool ParamTraits<base::FileDescriptor>::Read(const base::Pickle* m,
   if (!m->ReadAttachment(iter, &attachment))
     return false;
 
+  if (static_cast<MessageAttachment*>(attachment.get())->GetType() !=
+      MessageAttachment::Type::PLATFORM_FILE) {
+    return false;
+  }
+
   *r = base::FileDescriptor(
-      static_cast<MessageAttachment*>(attachment.get())->TakePlatformFile(),
+      static_cast<internal::PlatformFileAttachment*>(attachment.get())
+          ->TakePlatformFile(),
       true);
   return true;
 }