repl: Failed to save editor mode text in `.save`

Fixes: https://github.com/nodejs/node/issues/8142
PR-URL: https://github.com/nodejs/node/pull/8145
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/repl.js

@@ -471,6 +471,7 @@ function REPLServer(prompt,
 
     if (self.editorMode) {
       self.bufferedCommand += cmd + '\n';
+      self.memory(cmd);
       return;
     }
 

test/parallel/test-repl-.save.load.js

@@ -29,6 +29,26 @@ putIn.run(['.save ' + saveFileName]);
 // the file should have what I wrote
 assert.equal(fs.readFileSync(saveFileName, 'utf8'), testFile.join('\n') + '\n');
 
+{
+  // save .editor mode code
+  const cmds = [
+    'function testSave() {',
+    'return "saved";',
+    '}'
+  ];
+  const putIn = new common.ArrayStream();
+  const replServer = repl.start('', putIn);
+
+  putIn.run(['.editor']);
+  putIn.run(cmds);
+  replServer.write('', {ctrl: true, name: 'd'});
+
+  putIn.run([`.save ${saveFileName}`]);
+  replServer.close();
+  assert.strictEqual(fs.readFileSync(saveFileName, 'utf8'),
+                     `${cmds.join('\n')}\n`);
+}
+
 // make sure that the REPL data is "correct"
 // so when I load it back I know I'm good
 testMe.complete('inner.o', function(error, data) {