http2: Do not imply a callback to compat res.write

Fixes: #135

Author: mcollina

lib/internal/http2/compat.js

@@ -417,7 +417,11 @@ class Http2ServerResponse extends Stream {
   write(chunk, encoding, cb) {
     var stream = this[kStream];
     if (stream === undefined) {
-      cb(new Error('HTTP/2 Stream has been closed'));
+      var err = new Error('HTTP/2 Stream has been closed');
+      if (cb)
+        cb(err);
+      else
+        this.emit('error', err);
       return;
     }
     var beginSend = this[kBeginSend];

test/parallel/test-http2-compat-serverresponse-write-no-cb.js

@@ -0,0 +1,35 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const h2 = require('http2');
+
+// Http2ServerResponse.write does not imply there is a callback
+
+const server = h2.createServer();
+server.listen(0, common.mustCall(function() {
+  const port = server.address().port;
+  const url = `http://localhost:${port}`;
+  const client = h2.connect(url, common.mustCall(function() {
+    const headers = {
+      ':path': '/',
+      ':method': 'GET',
+      ':scheme': 'http',
+      ':authority': `localhost:${port}`
+    };
+    const request = client.request(headers);
+    request.end();
+    request.resume();
+  }));
+
+  server.once('request', common.mustCall(function(request, response) {
+    client.destroy();
+    setImmediate(function() {
+      response.on('error', common.mustCall(function(err) {
+        assert.strictEqual(err.message, 'HTTP/2 Stream has been closed');
+      }));
+      response.write('muahaha');
+      server.close();
+    });
+  }));
+}));