[Regression Fix] Readd timeline caching

[Mikescops]

Fixing a regression following #468 after update of the vue-virtual-grid package.

The caching of the timeline is now used again. It helped simplifying some part of the logic too.

[Mikescops]

@skjnldsv done

[skjnldsv]

Tiny change, all good code-wise :)
One question though, why use Promise.resolve ?
Returning should be enough in those cases,

[Mikescops]

The lib expect a Promise so that it can do other actions in the meantime.

[skjnldsv]

The lib expect a Promise so that it can do other actions in the meantime.

The async function resolves themselves with return or throw.
Async functions are already promises :)

[skjnldsv]

This returns a promise:

function resolveAfter2Seconds() {
  return new Promise(resolve => {
    setTimeout(() => {
      resolve('resolved');
    }, 2000);
  });
}

Promise.resolve have no context here. I don't think that is necessary

[Mikescops]

hmmm I need to better look at it