test: add http _dump regression test

Test part of 299da1f, specifically for v8.x.

PR-URL: #21595
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: addaleax

test/parallel/test-http-pause-no-dump.js

@@ -0,0 +1,33 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+
+const server = http.createServer(common.mustCall(function(req, res) {
+  req.once('data', common.mustCall(() => {
+    req.pause();
+    res.writeHead(200);
+    res.end();
+    res.on('finish', common.mustCall(() => {
+      assert(!req._dumped);
+    }));
+  }));
+}));
+server.listen(0);
+
+server.on('listening', common.mustCall(function() {
+  const req = http.request({
+    port: this.address().port,
+    method: 'POST',
+    path: '/'
+  }, common.mustCall(function(res) {
+    assert.strictEqual(res.statusCode, 200);
+    res.resume();
+    res.on('end', common.mustCall(() => {
+      server.close();
+    }));
+  }));
+
+  req.end(Buffer.allocUnsafe(1024));
+}));