http: specify _implicitHeader in OutgoingMessage

PR-URL: #7949
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/_http_outgoing.js

@@ -413,6 +413,9 @@ OutgoingMessage.prototype._renderHeaders = function() {
   return headers;
 };
 
+OutgoingMessage.prototype._implicitHeader = function() {
+  throw new Error('_implicitHeader() method is not implemented');
+};
 
 Object.defineProperty(OutgoingMessage.prototype, 'headersSent', {
   configurable: true,

test/parallel/test-http-outgoing-proto.js

@@ -0,0 +1,14 @@
+'use strict';
+require('../common');
+const assert = require('assert');
+
+const http = require('http');
+const OutgoingMessage = http.OutgoingMessage;
+const ClientRequest = http.ClientRequest;
+const ServerResponse = http.ServerResponse;
+
+assert.throws(OutgoingMessage.prototype._implicitHeader);
+assert.strictEqual(
+  typeof ClientRequest.prototype._implicitHeader, 'function');
+assert.strictEqual(
+  typeof ServerResponse.prototype._implicitHeader, 'function');