Hopefully get rid of FrameProducer._stop() timeouts. Doesn't reproduce locally.

lib/util/riskystream.js

@@ -1,5 +1,6 @@
 var util = require('util')
 
+var Promise = require('bluebird')
 var EventEmitter = require('eventemitter3').EventEmitter
 
 function RiskyStream(stream) {
@@ -34,4 +35,27 @@ RiskyStream.prototype.expectEnd = function() {
   return this
 }
 
+RiskyStream.prototype.waitForEnd = function() {
+  var stream = this.stream
+    , endListener
+
+  this.expectEnd()
+
+  return new Promise(function(resolve/*, reject*/) {
+      if (stream.ended) {
+        return resolve(true)
+      }
+
+      stream.on('end', endListener = function() {
+        resolve(true)
+      })
+
+      // Make sure we actually have a chance to get the 'end' event.
+      stream.resume()
+    })
+    .finally(function() {
+      stream.removeListener('end', endListener)
+    })
+}
+
 module.exports = RiskyStream