Avoid allocating Runnable wrapper

core/src/main/scala/org/scalajs/macrotaskexecutor/MacrotaskExecutor.scala

@@ -29,15 +29,15 @@ object MacrotaskExecutor extends ExecutionContextExecutor {
  private[this] final val Undefined = "undefined"
 
  def execute(runnable: Runnable): Unit =
- setImmediate(() => runnable.run())
+ setImmediate(runnable)
 
  def reportFailure(cause: Throwable): Unit =
  cause.printStackTrace()
 
- private[this] val setImmediate: (() => Unit) => Unit = {
+ private[this] val setImmediate: Runnable => Unit = {
  if (js.typeOf(js.Dynamic.global.setImmediate) == Undefined) {
  var nextHandle = 1
- val tasksByHandle = mutable.Map[Int, () => Unit]()
+ val tasksByHandle = mutable.Map[Int, Runnable]()
  var currentlyRunningATask = false
 
  def canUsePostMessage(): Boolean = {
@@ -71,7 +71,7 @@ object MacrotaskExecutor extends ExecutionContextExecutor {
  case Some(task) =>
  currentlyRunningATask = true
  try {
- task()
+ task.run()
  } finally {
  tasksByHandle -= handle
  currentlyRunningATask = false
@@ -95,7 +95,7 @@ object MacrotaskExecutor extends ExecutionContextExecutor {
  js.Dynamic.global.Node.constructor("return setImmediate")()
 
  { k =>
- setImmediate(k)
+ setImmediate(() => k.run())
  ()
  }
  } else if (canUsePostMessage()) {
@@ -153,13 +153,13 @@ object MacrotaskExecutor extends ExecutionContextExecutor {
  // we're also not going to bother fast-pathing for IE6; just fall through
 
  { k =>
- js.Dynamic.global.setTimeout(k, 0)
+ js.Dynamic.global.setTimeout(() => k.run(), 0)
  ()
  }
  }
  } else {
  { k =>
- js.Dynamic.global.setImmediate(k)
+ js.Dynamic.global.setImmediate(() => k.run())
  ()
  }
  }