http: Use OOP for OutgoingMessage._finish

Sniffing instanceof a child class in the parent class's method
is Doing It Wrong.

lib/_http_client.js

@@ -133,6 +133,12 @@ util.inherits(ClientRequest, OutgoingMessage);
 
 exports.ClientRequest = ClientRequest;
 
+ClientRequest.prototype._finish = function() {
+  DTRACE_HTTP_CLIENT_REQUEST(this, this.connection);
+  COUNTER_HTTP_CLIENT_REQUEST();
+  OutgoingMessage.prototype._finish.call(this);
+};
+
 ClientRequest.prototype._implicitHeader = function() {
   this._storeHeader(this.method + ' ' + this.path + ' HTTP/1.1\r\n',
                     this._renderHeaders());

lib/_http_outgoing.js

@@ -515,25 +515,8 @@ OutgoingMessage.prototype.end = function(data, encoding) {
 };
 
 
-var ServerResponse, ClientRequest;
-
 OutgoingMessage.prototype._finish = function() {
   assert(this.connection);
-
-  if (!ServerResponse)
-    ServerResponse = require('_http_server').ServerResponse;
-
-  if (!ClientRequest)
-    ClientRequest = require('_http_client').ClientRequest;
-
-  if (this instanceof ServerResponse) {
-    DTRACE_HTTP_SERVER_RESPONSE(this.connection);
-    COUNTER_HTTP_SERVER_RESPONSE();
-  } else {
-    assert(this instanceof ClientRequest);
-    DTRACE_HTTP_CLIENT_REQUEST(this, this.connection);
-    COUNTER_HTTP_CLIENT_REQUEST();
-  }
   this.emit('finish');
 };
 

lib/_http_server.js

@@ -111,6 +111,13 @@ function ServerResponse(req) {
 }
 util.inherits(ServerResponse, OutgoingMessage);
 
+ServerResponse.prototype._finish = function() {
+  DTRACE_HTTP_SERVER_RESPONSE(this.connection);
+  COUNTER_HTTP_SERVER_RESPONSE();
+  OutgoingMessage.prototype._finish.call(this);
+};
+
+
 
 exports.ServerResponse = ServerResponse;