meta refresh waiting is broken

[TimothyGu]

In the shared declarative refresh steps, there is a step that does

After the refresh has come due (as defined below), ... navigate document's browsing context to urlRecord, with ...

For the purposes of the previous paragraph, a refresh is said to have come due as soon as the later of the following two conditions occurs:

• At least time seconds have elapsed since document has completely loaded, adjusted to take into account user or user agent preferences.
• If meta is given, at least time seconds have elapsed since meta was inserted into the document document, adjusted to take into account user or user agent preferences.

We should define this more precisely, perhaps similar to how timer initialization steps. In particular, two things need to be clarified:

• The waiting should be done in parallel.
• The navigation should be queued in a task, even for content=0, in which case the task is queued immediately without being queued in parallel.