Mojo bindings: merge the control messages of sending disconnect reason and notifying endpoint close…

mojo/public/cpp/bindings/pipe_control_message_proxy.h

Index: mojo/public/cpp/bindings/pipe_control_message_proxy.h
diff --git a/mojo/public/cpp/bindings/pipe_control_message_proxy.h b/mojo/public/cpp/bindings/pipe_control_message_proxy.h
index f5da26b7493a2f23daec6b1b0ab22dc11a2e0128..24005c2f93ff209bd69f1467e6b6328192a84ad6 100644
--- a/mojo/public/cpp/bindings/pipe_control_message_proxy.h
+++ b/mojo/public/cpp/bindings/pipe_control_message_proxy.h
@@ -6,9 +6,12 @@
 #define MOJO_PUBLIC_CPP_BINDINGS_PIPE_CONTROL_MESSAGE_PROXY_H_
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "mojo/public/cpp/bindings/bindings_export.h"
+#include "mojo/public/cpp/bindings/disconnect_reason.h"
 #include "mojo/public/cpp/bindings/interface_id.h"
 #include "mojo/public/cpp/bindings/lib/serialization_context.h"
+#include "mojo/public/cpp/bindings/message.h"
 
 namespace mojo {
 
@@ -23,9 +26,14 @@ class MOJO_CPP_BINDINGS_EXPORT PipeControlMessageProxy {
   // be used from multiple threads, |receiver| must be thread-safe.
   explicit PipeControlMessageProxy(MessageReceiver* receiver);
 
-  void NotifyPeerEndpointClosed(InterfaceId id);
+  void NotifyPeerEndpointClosed(InterfaceId id,
+                                const base::Optional<DisconnectReason>& reason);
   void NotifyEndpointClosedBeforeSent(InterfaceId id);
 
+  static Message ConstructPeerEndpointClosedMessage(
+      InterfaceId id,
+      const base::Optional<DisconnectReason>& reason);
+
  private:
   // Not owned.
   MessageReceiver* receiver_;