tty: make readStream.setRawMode() return this

PR-URL: #22950
Fixes: #22916
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>

doc/api/tty.md

@@ -64,6 +64,7 @@ added: v0.7.7
   raw device. If `false`, configures the `tty.ReadStream` to operate in its
   default mode. The `readStream.isRaw` property will be set to the resulting
   mode.
+* Returns: {this} - the read stream instance.
 
 Allows configuration of `tty.ReadStream` so that it operates as a raw device.
 

lib/tty.js

@@ -71,9 +71,10 @@ ReadStream.prototype.setRawMode = function(flag) {
   const err = this._handle.setRawMode(flag);
   if (err) {
     this.emit('error', errors.errnoException(err, 'setRawMode'));
-    return;
+    return this;
   }
   this.isRaw = flag;
+  return this;
 };
 
 function WriteStream(fd) {