Mojo C++ bindings: Simplify associated interface API.

mojo/public/interfaces/bindings/pipe_control_messages.mojom

Index: mojo/public/interfaces/bindings/pipe_control_messages.mojom
diff --git a/mojo/public/interfaces/bindings/pipe_control_messages.mojom b/mojo/public/interfaces/bindings/pipe_control_messages.mojom
index df3c43bb1aceb04273c6dc0b09e35be42ee5f1ba..74e9cc7657b9d8724d485afc5b82595b4b06f49a 100644
--- a/mojo/public/interfaces/bindings/pipe_control_messages.mojom
+++ b/mojo/public/interfaces/bindings/pipe_control_messages.mojom
@@ -25,8 +25,6 @@ struct RunOrClosePipeMessageParams {
 
 union RunOrClosePipeInput {
   PeerAssociatedEndpointClosedEvent peer_associated_endpoint_closed_event;
-  AssociatedEndpointClosedBeforeSentEvent
-      associated_endpoint_closed_before_sent_event;
 };
 
 // A user-defined reason about why the interface is disconnected.
@@ -37,7 +35,7 @@ struct DisconnectReason {
 
 // An event to notify that an interface endpoint set up at the message sender
 // side has been closed.
-// 
+//
 // This event is omitted if the endpoint belongs to the master interface and
 // there is no disconnect reason specified.
 struct PeerAssociatedEndpointClosedEvent {
@@ -46,12 +44,3 @@ struct PeerAssociatedEndpointClosedEvent {
   DisconnectReason? disconnect_reason;
 };
 
-// An event to notify that an interface endpoint that is meant to be set up at
-// the message receiver side has been closed before sent over the message pipe.
-//
-// This event is only used for associated interfaces.
-struct AssociatedEndpointClosedBeforeSentEvent {
-  // The interface ID.
-  uint32 id;
-};
-