Merge lp://staging/~rvb/launchpad/dds-fix-spinner-50391 into lp://staging/launchpad

This branch looks good.

As for testing, it would be sufficient to check that the nodes selected
are correct. The easiest way I can see to do that would be to do a
small refactoring such that the code to select the node to apply the
animation to is in its own function. You can then call the function and
verify that the element is of the right description (e.g., class).

I don't know if there's a practical difference between the two, but I've
seen us use .empty() more often than .set('innerHTML',''). Also,
.empty() is chainable, so instead of

    var placeholder = container.one('.package-diff-placeholder');
    placeholder.set('innerHTML','');
    placeholder.appendChild(in_progress_message);

you could do (note the removal of "var placeholder"):

    container.one('.package-diff-placeholder')
        .empty()
        .append(in_progress_message);

Here are a couple of tiny whitespace fixes:

- container.append(in_progress_message);
- container.one('.package-diff-placeholder').set(
- 'text',
- 'Differences from last common version:');
+ var placeholder = container.one('.package-diff-placeholder');
+ placeholder.set('innerHTML','');

There is a missing space after the comma.

+ placeholder.appendChild(in_progress_message);
     var success_cb = function(transaction_id, response, args) {
         container.one('p.update-in-progress-message').remove();
+ container.one('.package-diff-placeholder').set(
+ 'text',
+ 'Differences from last common version:');
         container.all('.request-derived-diff').each(function(sub_container){

The above line wasn't changed in your branch, but it needs a space
before the open brace.

Fixed. Thanks for the review.