"Checked by default" categories always checked when pop-up opens, even if user unchecked

Problem/Motivation

Counter-intuitive behaviour; see issue title.

Steps to reproduce

1. Set up some categories, and make at least one "Checked by default".
2. Go to a page where the pop-up can be opened, and open it. Checked by default category will be checked, as expected without any choice yet made. Uncheck that category and save preferences.
3. Open the pop-up again. Notice that the checked by default category is now checked again, even though you unchecked it.

Proposed resolution

After some digging, I noticed that the HTML for the pop-up starts out with the checked attribute applied to the category checkboxes that are to be checked by default, which makes sense. Then I looked through the JavaScript code and noticed that Drupal.eu_cookie_compliance.setPreferenceCheckboxes() only sets the checked DOM property to true on the checkboxes for the categories the user has agreed to, but doesn't touch the ones that weren't agreed to. I'm not familiar with the JavaScript for this, but I'm guessing it's doing something that replaces the DOM tree with the default markup, thus likely obliterating the state of the checkboxes each time the pop-up opens, in which case browsers naturally fall back to using the checked HTML attribute to determine the initial

Remaining tasks

This is the current method:

  Drupal.eu_cookie_compliance.setPreferenceCheckboxes = function (categories) {
    for (var i in categories) {
      $("#eu-cookie-compliance-categories input:checkbox[value='" + categories[i] + "']").prop("checked", true);
    }
  }

The problem is that categories only contains the agreed to categories. This seems to fix it:

  Drupal.eu_cookie_compliance.setPreferenceCheckboxes = function (categories) {
    // Set all checkboxes to unchecked before applying existing categories so
    // checked by default categories that weren't agreed to correctly display
    // their saved state.
    $("#eu-cookie-compliance-categories input:checkbox").prop("checked", false);

    for (var i in categories) {
      $("#eu-cookie-compliance-categories input:checkbox[value='" + categories[i] + "']").prop("checked", true);
    }
  }

User interface changes

None?

API changes

Probably none?

Data model changes

None?