timers: fix unref() memory leak

lib/timers.js

@@ -301,6 +301,14 @@ const Timeout = function(after) {
   this._repeat = null;
 };
 
+
+function unrefdHandle() {
+  this.owner._onTimeout();
+  if (!this.owner._repeat)
+    this.owner.close();
+}
+
+
 Timeout.prototype.unref = function() {
   if (this._handle) {
     this._handle.unref();
@@ -315,7 +323,8 @@ Timeout.prototype.unref = function() {
     if (this._called && !this._repeat) return;
 
     this._handle = new Timer();
-    this._handle[kOnTimeout] = this._onTimeout;
+    this._handle.owner = this;
+    this._handle[kOnTimeout] = unrefdHandle;
     this._handle.start(delay, 0);
     this._handle.domain = this.domain;
     this._handle.unref();

test/parallel/test-timers-unrefd-interval-still-fires.js

@@ -0,0 +1,18 @@
+/*
+ * This test is a regression test for joyent/node#8900.
+ */
+var assert = require('assert');
+
+var N = 5;
+var nbIntervalFired = 0;
+var timer = setInterval(function() {
+  ++nbIntervalFired;
+  if (nbIntervalFired === N)
+    clearInterval(timer);
+}, 1);
+
+timer.unref();
+
+setTimeout(function onTimeout() {
+  assert.strictEqual(nbIntervalFired, N);
+}, 100);