Mojo C++ bindings: Simplify associated interface API.

mojo/public/interfaces/bindings/pipe_control_messages.mojom

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [JavaPackage="org.chromium.mojo.bindings.pipecontrol"]
 module mojo.pipe_control;
 
 // For each message pipe running user-defined interfaces, some control
 // functions are provided and used by the routers at both ends of the pipe, so
 // that they can coordinate to manage interface endpoints.
 // All these control messages will have the interface ID field in the message
 // header set to invalid.
 
 ////////////////////////////////////////////////////////////////////////////////
 // RunOrClosePipe@0xFFFFFFFE(RunOrClosePipeInput input);
 //
 // This control function runs the input command. If the operation fails or the
 // command is not supported, the message pipe is closed.
 
 const uint32 kRunOrClosePipeMessageId = 0xFFFFFFFE;
 
 struct RunOrClosePipeMessageParams {
   RunOrClosePipeInput input;
 };
 
 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.
 struct DisconnectReason {
   uint32 custom_reason;
   string description;
 };
 
 // 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 {
   // The interface ID.
   uint32 id;
   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;
-};
-