child_process: move anonymous class to top level

Move the anonymous class out of setupChannel to clarify code.

PR-URL: https://github.com/nodejs/node/pull/11147
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/internal/child_process.js

@@ -407,22 +407,8 @@ ChildProcess.prototype.unref = function() {
   if (this._handle) this._handle.unref();
 };
 
-
-function setupChannel(target, channel) {
-  target.channel = channel;
-
-  // _channel can be deprecated in version 8
-  Object.defineProperty(target, '_channel', {
-    get() { return target.channel; },
-    set(val) { target.channel = val; },
-    enumerable: true
-  });
-
-  target._handleQueue = null;
-  target._pendingHandle = null;
-
-  const control = new class extends EventEmitter {
-    constructor() {
+class Control extends EventEmitter {
+  constructor(channel) {
     super();
     this.channel = channel;
     this.refs = 0;
@@ -438,7 +424,22 @@ function setupChannel(target, channel) {
       this.emit('unref');
     }
   }
-  }();
+}
+
+function setupChannel(target, channel) {
+  target.channel = channel;
+
+  // _channel can be deprecated in version 8
+  Object.defineProperty(target, '_channel', {
+    get() { return target.channel; },
+    set(val) { target.channel = val; },
+    enumerable: true
+  });
+
+  target._handleQueue = null;
+  target._pendingHandle = null;
+
+  const control = new Control(channel);
 
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