Adding a link to a drupal media item does not trigger CKEditor's change event

Problem/Motivation

The Editor module tracks when an editor has modified a field, and reverts the value of a field when its editor has not made any changes. When simply adding a link to a Drupal Media item in CKEditor, the "change" event is not fired and the field is not flagged as having been changed, which will cause the field to be reverted in some conditions. Strangely, the "change" event is correctly fired when adding a link to a Drupal Image item.

Steps to reproduce

1. Edit a node with a body field that uses CKEditor with the Drupal Media CKEditor plugin enabled.
2. Add media to your content.
3. Save the node, then go back to the edit screen.
4. Click on the Drupal Media item, then click the link icon in the CKEditor toolbar and add a link to wrap the media item.
5. Use the code inspector to inspect the accompanying, hidden textarea (its name will be "body[0][value]").
6. The "data-editor-value-is-changed" attribute should be "true", but is not.
7. Make any other changes to content -- add a line break, add some text, etc.
8. Inspect the textarea again. The "data-editor-value-is-changed" is now correctly set to "true".

Proposed resolution

Add code to the Drupal Media CKEditor plugin to correctly fire the "change" event when the link value is changed.

Remaining tasks

Develop and test.

User interface changes

n/a

API changes

n/a

Data model changes

n/a

Release notes snippet

n/a