net: fix bufferSize include writableStream length

socket.bufferSize missed to include the length of internal buffers in
writableStream.

lib/net.js

@@ -325,7 +325,7 @@ Object.defineProperty(Socket.prototype, 'readyState', {
 Object.defineProperty(Socket.prototype, 'bufferSize', {
   get: function() {
     if (this._handle) {
-      return this._handle.writeQueueSize;
+      return this._handle.writeQueueSize + this._writableState.length;
     }
   }
 });

test/simple/test-net-buffersize.js

@@ -0,0 +1,51 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var net = require('net');
+
+var iter = 10;
+
+var server = net.createServer(function(socket) {
+  socket.on('readable', function() {
+    socket.read();
+  });
+
+  socket.on('end', function() {
+    server.close();
+  });
+});
+
+server.listen(common.PORT, function() {
+  var client = net.connect(common.PORT);
+
+  client.on('finish', function() {
+    assert.strictEqual(client.bufferSize, 0);
+  });
+
+  for (var i = 1; i < iter; i++) {
+    client.write('a');
+    assert.strictEqual(client.bufferSize, i);
+  }
+
+  client.end();
+});