@Mooeypoo or @Tchanders to fill in description.

It seems there are two points at which we need to show the loading bar:

1. while the JS widget is loading, if the user has JS
2. while the menu is loading, after the input has been changed

After speaking to @Mooeypoo it seems this task is about point 2, so I've updated the description.

It seems that this is already working, and there's nothing to fix. Testing with network throttling, I see:

In T209630#4765596, @Tchanders wrote:

It seems there are two points at which we need to show the loading bar:

1. while the JS widget is loading, if the user has JS
2. while the menu is loading, after the input has been changed

After speaking to @Mooeypoo it seems this task is about point 2

Point 1 filed as T210080