Plugin Lazy loading can cause usort warning

Problem/Motivation

Sporadically we get the following warning:
Warning: uasort(): Array was modified by the user comparison function in Drupal\Core\Plugin\DefaultLazyPluginCollection->sort() (line 100 of core/lib/Drupal/Core/Plugin/DefaultLazyPluginCollection.php).

A 100% repo is to use the "Entity Browser Module" when using a file field (in our case inside a field collection) with the File Browser widget.

Proposed resolution

According to this link:
http://shout.setfive.com/2013/06/14/symfony2-usort-array-was-modified-by...

The problem lies in the lazy loading of the plugin collection. So the fix is simple. In the sort() function (DefaultLazyLoadingPluginCollection) iterate through the array like this:

  public function sort() {
    // iterate to populatae the array
    foreach($this->instanceIDs as $id){
      $pluginId = $this->get($id)->getPluginId();
    }
    // original code
    uasort($this->instanceIDs, array($this, 'sortHelper'));
    return $this;
  }

Remaining tasks

reviews needed, tests to be written and run

User interface changes

none

API changes

none

Data model changes

none

Original report by [username]

none